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Old 03-14-2017, 06:33 AM   #1
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AUX Solenoid Change Allows Alternator To Charge House Batteries - Good Idea or NOT???

Reading other posts about fixing bad solenoids eventually morphed into how you can change your AUX Switch control solenoid so your engine alternator can charge your house batteries when you are driving down the road.

Is this a good idea? I have some questions and need help from a more experienced RV electrician/mechanic.

How is this accomplished? Answer: You change the Continuous Duty Solenoid controlled by your AUX Switch from a pull-in voltage of 12V that is original equipment to 7.5V. That's it.

How does that accomplish the goal of letting your alternator charge your house batteries?

Answer: Since the house batteries never go below 9v, but often vary between 11.5 and 12.8 when you are driving down the road; I conclude the solenoid is always on or "pulled-in" and this completes the circuit from the alternator through the AUX solenoid (and through the coach Battery Disconnect Switch Solenoid) to the house batteries. ...And I presume the ignition key switch needs to be turned on as well, which makes sense since it's assumed the engine is running for the alternator to work.

(I am told you can use a 3 post continuous duty solenoid or a 4 post solenoid by adding a ground wire to the frame, but you should make sure you buy only those solenoids of high quality and that means they must have silver contacts and not copper contacts... which is why not any automotive solenoid will work. I am told Napa carries one with 4 posts called an ST80 12V, 4 terminals, insulated base, flat bracket, silver contacts, continuous duty for extended engagement, low current coil 16-21 ohms, 7.5V pull in voltage, about $59. And the RV dealer sells a similar type for over $200.)

But is this a good idea? And I make these assumptions:

* I assume my house batteries will be charging at whatever rate the alternator is putting out... with max out at 80A or 100A depending on the size of your alternator. Is that correct?

* My big question is this: When the coach is parked and the engine is turned off... and the ignition key if off... is the engine battery still connected to the house battery? Even in the least bit?

I'm concerned, because if you have any parasitic drain on the engine battery... like a faulty front step or a light that gets left on by mistake... or a short in the chassis side... Will that pull down the house battery too?

And what about a problem with the DC house batteries, i.e., if there is a short on the house side of the circuit, will that pull down the engine battery?

* And how does changing out Solenoid types (7.5V pull-in type in place of 12V) compare to adding an Auto Charge Relay like this one from Blue Sea?

https://www.bluesea.com/products/761...2V_24V_DC_120A

PS At first glance, I'm not a fan of the digital Automatic Charging Relay, because of shorts directly in my battery box and that could cause a fire, but I have not heard of this problem.

Thank you for your wisdom! I think I favor the "Solenoid Swap" but I would be interested other opinions based on testimonials or from professionals.
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Old 03-14-2017, 07:15 AM   #2
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If you have a diesel MH install a B.I.R.D
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Old 03-14-2017, 07:29 AM   #3
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I'm not sure why your rig doesn't already have this feature installed. 99.9% of MHs do.

Some are key actavated and others your voltage sensing relays to control the solenoid.

Some pre 2000 MHs use a diode based isolator to split the alternator output.

There are many VSRs out there.

Yandina.com, Cyrix Combiner, Blue Sea, and the one mentioned before by Interlictit.

You may already have this feature but it's not working.
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Old 03-14-2017, 08:29 AM   #4
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What difference does changing from a 12v solenoid to a 7.5v solenoid make? Your MH already charges your house batteries from your alternator through a simple 12v battery isolator solenoid that is closed (pulled in) when your ignition turns on. Every (or at least nearly every) RV made since at least the '70's is set up that way, although newer rigs may have a more complicated setup, as twinboat said. I can't help but wonder if you are inventing a solution for a problem that doesn't exist. And if your coach ISN'T already set up like this, then the addition of a simple continuous duty 12v relay activated by your ignition is all that's needed to accomplish the task: Ignition ON; house & chassis batteries are connected and charged from alternator. Ignition OFF; house & chassis batteries are isolated from each other.
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Old 03-14-2017, 09:28 AM   #5
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imnprsd-

First off,

:welcome:

Second, what year, make and model of RV do you have?

Third, you should put that information in a "signature." A "signature" save you having to tell folks that info each time. Here's a link on how to do that.
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Old 03-14-2017, 06:43 PM   #6
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UPDATE TO ORIGINAL THREAD w/ SOLUTION

UPDATE TO MY POSTING:

My RV is a 2004 Itasca Horizon Diesel ISK40SD model, and my 2 solenoids are located behind a heavy metal enclosure, next to the inverter/charger... where it gets hot inside (I think).

…And after much research, I feel reasonably confident the following information is accurate.

In my system I have 2 different types of solenoids:

1) Battery Disconnect Solenoid: Winne Part #086273-01-000 replacement alternatives: Intelletec Part# 01-00055-000, and you find this part on Amizon.com:

https://www.amazon.com/Intellitec-Ba...QP980XGCKXDFY8

2) AUX/Boost type solenoid: Winne Part #: 8188-02-000 replacement alternatives: Trombetta # 114-1211-020 is equivalent to Camdec 18226-WR. The 12 means a 12 volt coil and the 02 means silver contacts.

Amazon to find your AUX/Boost type solenoid:

https://www.amazon.com/gp/product/B0...re-bullets-btf

Note: The Winne OEM is a 3-pole type and the Trombetta or Camdec type has a 4th terminal you use for ground. (Just run another wire.) But the other concern is that these types of Solenoids are wider than your OEM type (TBD) and may need you to drill a wide hole to mount. However, from everything I have read that is worth the extra effort.

REVIEW OF TOPICS

* House battery charging systems vary by manufacture and year of your RV. Most use an AUX/Boost Solenoid wiring (with and through the Battery Disconnect Solenoid) that will allow your alternator to charge your house batteries; but other designs (pre-2004/5 vs post 2005 for example) may use the so-called B.I.R.D. system, and still other RV modes may even uses your inverter/charger to trickle charge your house battery as you roll down the road. Remember, the thought back then was that you are not using much house VDC when you are driving.

…But with today’s coaches utilizing residential refrigerators (like I now have), we very much want our alternator to charge the house battery while we are driving down the road. Why? Because after 3-4 hours on the road it would be desirable to have a full house battery bank when I pull into a Wallmart overnight and need to use the house gas heater & DC fan for most of the night, because it’s cold outside. Plus it would be nice to have enough battery power to watch an hour of TV, or maybe cook something in the microwave. (Yikes! When you think of the power it uses and your batteries are not above 50%.)

So you really do want to use the alternator to charge your house batteries, and my coach does not seem to do that? Why? Will it could be by design or maybe one or both of my solenoids are getting old.

* Solenoids coils fail a lot due to heat. Therefore, I am no longer thinking it’s a good idea to change your AUX/BOOST Solenoid from a 12V pull-up type for a 7.5V pull-up, because voltage through the solenoid coil will be in the alternator voltage range (up to 14.8V at times) and will run continuous -- and this will produce added heat and early solenoid failure – at the worst time of course – which is when you are on the road.

* For more technical understanding of Solenoid Coil failure read this post:
Battery Boost/ Auxillary Start Solenoid Failures

* Very good, Continuous Duty solenoids, with silver alloy contacts are now available through Amazon & even some Walmart stores.

CONCLUSTIONS

== > It's a very, very good idea to change your OEM Aux/Boost Solenoid & your Battery Disconnect Solenoid to heavier duty types (with silver alloy contacts) if you coach is 5+ years old and you still have the OEM types installed. And you should definitely change both solenoids if your coach is 10+ years old.

== > If you alternator is not charging your house batteries then maybe one or both of your solenoid types are not working properly; i.e., the coil may work when you start the coach and for a period of time after that, but with continuous voltages of 14V+ heating up the 12V pull-up coil in the solenoid, then maybe the added heat & vibration (and therefore added resistance) is creating a failure after driving for a short period of time, but may still test good when you take it to the mechanic. Solution: Replace both types of Solenoids even though the culprit is probably just the AUX/Boost solenoid.

== > If your house batteries are dead after you store the RV for a week or longer, maybe your coils are partially fused to the contacts and current is being “leaked” away. Solution: Replace both types of Solenoids even though the Battery Disconnect Solenoid may be the culprit. Or if you have a B.I.R.D. system in your RV maybe it’s the problem? (Note: I suppose the key switch should also be checked.)

== > The last thing you need out on the road is a completely dead solenoid, because you may not allow you to start your engine at some point, which will turn into a nightmare if you are at a gas pump in the middle of no where. Solution: Do your homework and replace your 2 OEM solenoids (before your trip begins) with a heaver duty, silver contacts solenoid, and avoid getting stranded!!!

I hope this helps set the record straight, but testimonials are always appreciated and if a qualified mechanic can simplify why your alternator is not charging your house batteries; or why your house batteries are dead after you store your RV (even with the battery disconnect switch off) that would be great too!
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Old 03-15-2017, 04:16 PM   #7
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Every MH I've owned, 1979 Roll-a-Long, 1988 Jamboree, and now a 2004 Itasca, has used a solenoid to charge the house batteries from the alternator. I also, since 1989, have NEVER had one of the solenoids go bad, neither the Aux/Boost solenoid nor the Battery Cutoff solenoid. Oh, and those MHs were at least 10 years old when I purchased, and then used/driven for 10+ years after purchase. So I must disagree with your blanket statement that solenoids should be replaced at 5 years and MUST be replaced at 10 years. Not saying failures don't happen, and the thread you link to shows that it does, but I don't believe it's a widespread occurrence. YMMV.
BTW, on my first 2 MHs, the solenoids were under the hood (class C's), subject to alot of heat, no failures. My current Itasca (class A, gas), they are located under the step, no extra heat sources, no failures yet. My typical drive time is at least 3 hours non-stop.

If your's is not charging, then you need to find out what failed, rather than trying to come up with a new or modified system to do what it should already be doing (yes, I am confident that your RV is supposed to be charging your house batteries while driving).
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Old 03-15-2017, 05:18 PM   #8
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On my Journey the alternator does charge the engine and house batteries. The solenoids you reference are continuous duty rated and should last the life of the motorhome if used correctly.

In 25 years of RVing I've only heard of one person having a bad solenoid
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Old 03-15-2017, 06:35 PM   #9
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I have replaced the Trombetta charge solenoid on my 09 Journey three times. Appears that the contacts become pitted and charging not reliable. From my experience talking with other Winn owners, they also have experienced multiple failures as well. I carry a spare now as a failure wreaks havoc on my residential fridge. You are very lucky if your have the original.
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Old 03-15-2017, 06:38 PM   #10
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Quote:
Originally Posted by imnprsd View Post
UPDATE TO MY POSTING:

My RV is a 2004 Itasca Horizon Diesel ISK40SD model, and my 2 solenoids are located behind a heavy metal enclosure, next to the inverter/charger... where it gets hot inside (I think).

…And after much research, I feel reasonably confident the following information is accurate.

In my system I have 2 different types of solenoids:

1) Battery Disconnect Solenoid: Winne Part #086273-01-000 replacement alternatives: Intelletec Part# 01-00055-000, and you find this part on Amizon.com:

https://www.amazon.com/Intellitec-Ba...QP980XGCKXDFY8

2) AUX/Boost type solenoid: Winne Part #: 8188-02-000 replacement alternatives: Trombetta # 114-1211-020 is equivalent to Camdec 18226-WR. The 12 means a 12 volt coil and the 02 means silver contacts.

Amazon to find your AUX/Boost type solenoid:

https://www.amazon.com/gp/product/B0...re-bullets-btf

Note: The Winne OEM is a 3-pole type and the Trombetta or Camdec type has a 4th terminal you use for ground. (Just run another wire.) But the other concern is that these types of Solenoids are wider than your OEM type (TBD) and may need you to drill a wide hole to mount. However, from everything I have read that is worth the extra effort.

REVIEW OF TOPICS

* House battery charging systems vary by manufacture and year of your RV. Most use an AUX/Boost Solenoid wiring (with and through the Battery Disconnect Solenoid) that will allow your alternator to charge your house batteries; but other designs (pre-2004/5 vs post 2005 for example) may use the so-called B.I.R.D. system, and still other RV modes may even uses your inverter/charger to trickle charge your house battery as you roll down the road. Remember, the thought back then was that you are not using much house VDC when you are driving.

…But with today’s coaches utilizing residential refrigerators (like I now have), we very much want our alternator to charge the house battery while we are driving down the road. Why? Because after 3-4 hours on the road it would be desirable to have a full house battery bank when I pull into a Wallmart overnight and need to use the house gas heater & DC fan for most of the night, because it’s cold outside. Plus it would be nice to have enough battery power to watch an hour of TV, or maybe cook something in the microwave. (Yikes! When you think of the power it uses and your batteries are not above 50%.)

So you really do want to use the alternator to charge your house batteries, and my coach does not seem to do that? Why? Will it could be by design or maybe one or both of my solenoids are getting old.

* Solenoids coils fail a lot due to heat. Therefore, I am no longer thinking it’s a good idea to change your AUX/BOOST Solenoid from a 12V pull-up type for a 7.5V pull-up, because voltage through the solenoid coil will be in the alternator voltage range (up to 14.8V at times) and will run continuous -- and this will produce added heat and early solenoid failure – at the worst time of course – which is when you are on the road.

* For more technical understanding of Solenoid Coil failure read this post:
Battery Boost/ Auxillary Start Solenoid Failures

* Very good, Continuous Duty solenoids, with silver alloy contacts are now available through Amazon & even some Walmart stores.

CONCLUSTIONS

== > It's a very, very good idea to change your OEM Aux/Boost Solenoid & your Battery Disconnect Solenoid to heavier duty types (with silver alloy contacts) if you coach is 5+ years old and you still have the OEM types installed. And you should definitely change both solenoids if your coach is 10+ years old.

== > If you alternator is not charging your house batteries then maybe one or both of your solenoid types are not working properly; i.e., the coil may work when you start the coach and for a period of time after that, but with continuous voltages of 14V+ heating up the 12V pull-up coil in the solenoid, then maybe the added heat & vibration (and therefore added resistance) is creating a failure after driving for a short period of time, but may still test good when you take it to the mechanic. Solution: Replace both types of Solenoids even though the culprit is probably just the AUX/Boost solenoid.

== > If your house batteries are dead after you store the RV for a week or longer, maybe your coils are partially fused to the contacts and current is being “leaked” away. Solution: Replace both types of Solenoids even though the Battery Disconnect Solenoid may be the culprit. Or if you have a B.I.R.D. system in your RV maybe it’s the problem? (Note: I suppose the key switch should also be checked.)

== > The last thing you need out on the road is a completely dead solenoid, because you may not allow you to start your engine at some point, which will turn into a nightmare if you are at a gas pump in the middle of no where. Solution: Do your homework and replace your 2 OEM solenoids (before your trip begins) with a heaver duty, silver contacts solenoid, and avoid getting stranded!!!

I hope this helps set the record straight, but testimonials are always appreciated and if a qualified mechanic can simplify why your alternator is not charging your house batteries; or why your house batteries are dead after you store your RV (even with the battery disconnect switch off) that would be great too!
imnprsd,
First off, you're WAAAAAAAAAAAAY over thinking this. I, and many, many others on here have the EXACT SAME dual solenoid system you have on your coach. And yes, IT DOES charge the house batteries when you're cruising Americas roads. The Trombetta is HEAVY DUTY enough for that task. It's rated at, I think, around 100 or so amps but, not real sure. In any case, its heavy duty enough to handle charging duties of any type of house batteries.

https://www.amazon.com/Trombetta-12V...a+114-1211-010

There has been many, many threads on here about those solenoids and, various replacements for them. The primary reason they fail is because arcing and corrosion on the contact points. I've had mine apart twice for it and, both times, a little clean-up and, all was well. I eventually just ordered up a new one and, it's been fine too, ever since.

You don't need a "BIRD" or any other augmentation to your present system. Both of those solenoids are well placed and, do the job very adequately. Now, one thing that your system (and many like mine and more in that era) doesn't have is a way to charge your chassis batteries from shore power. There's a very, very simple answer to that without going into a whole scientific answer. It's called a Trik-L-Start and, unless one is hideously slow, it takes maybe, MAYBE around 1/2 an hour to install, especially in your case and the location of your two solenoids.

But, it's your coach and, you can do what ever you think is necessary to remedy what you think is a problem. A simple replacement of that Trombetta will cure your problem if, IF, there's no other problems in that part of the system.
Scott
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Old 03-16-2017, 12:10 PM   #11
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The supplied Trombetta solenoid is rated for 225 amps - more than the alternator peak output so it is properly sized. The copper contact solenoids have a design life of 25K operations and the silver contacts - twice that. I agree with Fire Up that you are over thinking this. Good luck
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Old 03-17-2017, 10:08 PM   #12
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I called a Trombetta distributor and spoke to a technical advisor, and here’s what he said:
“Sooner or later everyone ends up replacing their solenoids. It’s just a matter of when and where.”

Think about that for a minute!

…He then went on to say, “We are selling a ton of these solenoids and for a few extra dollars it pays to buy the silver alloy type.”

===

I would like to thank everyone for their feedback. Clearly there are a lot of owners who have experienced failed solenoids “on the road” and then later learn why they should have taken precautionary steps before they head out for their once in a year vacation. MAKE NO MISTAKE: YOUR SOLENOIDS ARE A CRITICAL PART and from what I can tell no one pays much attention to their solenoids until they have a critical failure.

So for these people and for everyone driving older RVs who want to do what they can for themselves and to ensure they have an uninterrupted family vacation, I will further summarize what I believe when it comes to RV solenoid replacement BEFORE THEY FAIL ON THE ROAD and at the worst possible time:

1) Your Aux/Boost solenoid is more prone to failure vs. your battery Disconnect Solenoid, but you might as well replace both at the same time and use a high quality type.

2) Don’t be fooled by the term “heavy duty”. Do your homework and don’t buy the brand; i.e., every brand makes lower and higher quality solenoids; and you just don’t know if your RV manufacture ordered the best OEM part or not until it fails and then they are all Sh*t!

4) Part numbers are important! And do NOT just ask for someone’s opinion at the parts counter. Ask for the best quality part and ask for the price difference for the other part-option (if you have a choice). This forces the mechanic or the parts supplier to give you options, and it gives you an opportunity to see if they technically know more than just to R&R a part, which helps build my confidence and makes me feel good about the cost of repair. That being said, don’t be afraid to go somewhere else if you need to; and I would even begin to go into everyone out there paying top-dollar for average quality parts!
Why? I guarantee there are times when you do NOT need to spend more money on your RV, and there are other time when you DEFINITELY SHOULD spend more money. This could not be more-true when it comes to diesel rigs in general, and in this post… when it comes to replacing solenoids.

For example: Tombetta’s “-020” type has the desirable silver alloy contacts, and the Tombetta “-010 has copper contacts that fail more frequently… and the silver types may only cost $3 more. (THAT WAS EASY!) So why some people will question the cost difference of a CRITICAL PART of your RV is beyond me… and for what… just a $3! Make no mistake, your solenoids are a CRITICAL PART of your RV and so is your battery management system, but it’s not easily understood, and it’s usually the last thing RV owners think about.

5) Diagrams are worth a thousand words. Here’s a typical, basic RV solenoid-battery-system. Please consult a schematic for your RV before you add a BIRD or auxiliary relay from Blue Sea if your coach design does not charge the house batteries while driving down the road.

6) AUX/BOOST switches also fail in the cockpit. So if you don’t get a “BOOST” when you need one, try operating the switch several times. This could save you when you most need saving! …And then replace the switch in time for your next RV trip or sooner.

7) Many times, if your house batteries are dead after storing them for just 3-4 weeks, your solenoids maybe the problem even if they function correctly and text “ok” by the tech.

It can also be said that your Inverter/Charger could be the culprit. So if you take the Inverter/Charger “out of the loop” and conduct an amp-meter test, you find there is indeed an internal short or leakage of current.

I suppose you could disconnect your positive battery terminal instead of going to the high cost and burden of repairing your Inverter/Charger that otherwise functions properly. Besides, it’s hard to find a repair person for these. And at over $2,000 to buy a new one… well you get the idea why this post is going to be very important to some more than others!

Thanks for reading. Over and out!
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Old 03-18-2017, 12:05 AM   #13
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Quote:
Originally Posted by imnprsd View Post
I called a Trombetta distributor and spoke to a technical advisor, and here’s what he said:
“Sooner or later everyone ends up replacing their solenoids. It’s just a matter of when and where.”

Think about that for a minute!

…He then went on to say, “We are selling a ton of these solenoids and for a few extra dollars it pays to buy the silver alloy type.”

===

I would like to thank everyone for their feedback. Clearly there are a lot of owners who have experienced failed solenoids “on the road” and then later learn why they should have taken precautionary steps before they head out for their once in a year vacation. MAKE NO MISTAKE: YOUR SOLENOIDS ARE A CRITICAL PART and from what I can tell no one pays much attention to their solenoids until they have a critical failure.

So for these people and for everyone driving older RVs who want to do what they can for themselves and to ensure they have an uninterrupted family vacation, I will further summarize what I believe when it comes to RV solenoid replacement BEFORE THEY FAIL ON THE ROAD and at the worst possible time:

1) Your Aux/Boost solenoid is more prone to failure vs. your battery Disconnect Solenoid, but you might as well replace both at the same time and use a high quality type.

2) Don’t be fooled by the term “heavy duty”. Do your homework and don’t buy the brand; i.e., every brand makes lower and higher quality solenoids; and you just don’t know if your RV manufacture ordered the best OEM part or not until it fails and then they are all Sh*t!

4) Part numbers are important! And do NOT just ask for someone’s opinion at the parts counter. Ask for the best quality part and ask for the price difference for the other part-option (if you have a choice). This forces the mechanic or the parts supplier to give you options, and it gives you an opportunity to see if they technically know more than just to R&R a part, which helps build my confidence and makes me feel good about the cost of repair. That being said, don’t be afraid to go somewhere else if you need to; and I would even begin to go into everyone out there paying top-dollar for average quality parts!
Why? I guarantee there are times when you do NOT need to spend more money on your RV, and there are other time when you DEFINITELY SHOULD spend more money. This could not be more-true when it comes to diesel rigs in general, and in this post… when it comes to replacing solenoids.

For example: Tombetta’s “-020” type has the desirable silver alloy contacts, and the Tombetta “-010 has copper contacts that fail more frequently… and the silver types may only cost $3 more. (THAT WAS EASY!) So why some people will question the cost difference of a CRITICAL PART of your RV is beyond me… and for what… just a $3! Make no mistake, your solenoids are a CRITICAL PART of your RV and so is your battery management system, but it’s not easily understood, and it’s usually the last thing RV owners think about.

5) Diagrams are worth a thousand words. Here’s a typical, basic RV solenoid-battery-system. Please consult a schematic for your RV before you add a BIRD or auxiliary relay from Blue Sea if your coach design does not charge the house batteries while driving down the road.

6) AUX/BOOST switches also fail in the cockpit. So if you don’t get a “BOOST” when you need one, try operating the switch several times. This could save you when you most need saving! …And then replace the switch in time for your next RV trip or sooner.

7) Many times, if your house batteries are dead after storing them for just 3-4 weeks, your solenoids maybe the problem even if they function correctly and text “ok” by the tech.

It can also be said that your Inverter/Charger could be the culprit. So if you take the Inverter/Charger “out of the loop” and conduct an amp-meter test, you find there is indeed an internal short or leakage of current.

I suppose you could disconnect your positive battery terminal instead of going to the high cost and burden of repairing your Inverter/Charger that otherwise functions properly. Besides, it’s hard to find a repair person for these. And at over $2,000 to buy a new one… well you get the idea why this post is going to be very important to some more than others!

Thanks for reading. Over and out!
imnprsd,
Just for grins Sir, our original Trombetta Auxiliary boost solenoid, lasted for ELEVEN YEARS and, 65,000 miles before starting to fail. That one was the copper contact version. I'd say that was pretty good reliability. The original battery shut down solenoid is now 12 years old and still works flawlessly. I do think like you in the fact that preventative maintenance is the key to a fun and happy RV life.
Scott
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Old 03-18-2017, 01:49 AM   #14
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Please google: "Simple RV Solenoid Diagrams" to find a general schematic
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Old 03-19-2017, 05:13 PM   #15
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Originally Posted by imnprsd View Post
Reading other posts about fixing bad solenoids eventually morphed into how you can change your AUX Switch control solenoid so your engine alternator can charge your house batteries when you are driving down the road.

Is this a good idea? I have some questions and need help from a more experienced RV electrician/mechanic.

How is this accomplished? Answer: You change the Continuous Duty Solenoid controlled by your AUX Switch from a pull-in voltage of 12V that is original equipment to 7.5V. That's it.

How does that accomplish the goal of letting your alternator charge your house batteries?

Answer: Since the house batteries never go below 9v, but often vary between 11.5 and 12.8 when you are driving down the road; I conclude the solenoid is always on or "pulled-in" and this completes the circuit from the alternator through the AUX solenoid (and through the coach Battery Disconnect Switch Solenoid) to the house batteries. ...And I presume the ignition key switch needs to be turned on as well, which makes sense since it's assumed the engine is running for the alternator to work.

(I am told you can use a 3 post continuous duty solenoid or a 4 post solenoid by adding a ground wire to the frame, but you should make sure you buy only those solenoids of high quality and that means they must have silver contacts and not copper contacts... which is why not any automotive solenoid will work. I am told Napa carries one with 4 posts called an ST80 12V, 4 terminals, insulated base, flat bracket, silver contacts, continuous duty for extended engagement, low current coil 16-21 ohms, 7.5V pull in voltage, about $59. And the RV dealer sells a similar type for over $200.)

But is this a good idea? And I make these assumptions:

* I assume my house batteries will be charging at whatever rate the alternator is putting out... with max out at 80A or 100A depending on the size of your alternator. Is that correct?

* My big question is this: When the coach is parked and the engine is turned off... and the ignition key if off... is the engine battery still connected to the house battery? Even in the least bit?

I'm concerned, because if you have any parasitic drain on the engine battery... like a faulty front step or a light that gets left on by mistake... or a short in the chassis side... Will that pull down the house battery too?

And what about a problem with the DC house batteries, i.e., if there is a short on the house side of the circuit, will that pull down the engine battery?

* And how does changing out Solenoid types (7.5V pull-in type in place of 12V) compare to adding an Auto Charge Relay like this one from Blue Sea?

https://www.bluesea.com/products/761...2V_24V_DC_120A

PS At first glance, I'm not a fan of the digital Automatic Charging Relay, because of shorts directly in my battery box and that could cause a fire, but I have not heard of this problem.

Thank you for your wisdom! I think I favor the "Solenoid Swap" but I would be interested other opinions based on testimonials or from professionals.
I am going to ask you to slow down, my friend. If both your coach and start batteries are NOT charging now while you are on the road you have a bad AUX solenoid. Look at this diagram from the Winnebago Resources page for your coach: http://www.winnebagoind.com/diagram/...ire_145020.pdf

On sheet 1, upper right quadrant you will see the AUX Start Solenoid. These can be had for about $15 up, depending where you get it, manufacturer, etc. High amp, 12V, continuous duty are the key factors. Silver contacts is a plus. Here is an example I found at Amizon: https://smile.amazon.com/CONTINUOUS-...words=solenoid

The unit may not look like the original but it does the same job. I replaced mine in my '05 Vectra. It was a pain to get to and the leads are not user friendly. If you do this yourself be certain to REMOVE the wires from the out feed of the battery banks (start/house). You don't want to do arc welding on the rig.

I hope this info helps. Happy trails.

Rick Y
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Old 03-19-2017, 06:30 PM   #16
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I've used this https://www.westmarine.com/buy/blue-...FcW6wAodk6wP3Q

on a couple of vehicles and recently got rid of the diode isolator on the Airstream and replaced it with the blue sea unit. Charging rate in to the house batteries with engine running is probably double what it was before, and it has the other advantage that on shore power or once the solar has caught up, the engine batteries are always fully charged
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Old 03-20-2017, 01:08 AM   #17
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The attached .pdf picture files should be closely examined to obtain a better understand how solenoids bridge your engine battery and isolate your 12V chassis system from your 12V house batteries.

These diagrams don't so much as answer how your house batteries get charged by the alternator when the engine is running, but they will let you know where your RV charging system circuit could be leaking current if one or both of your solenoids are old and not fully switching properly.
And don't forget your monentary AUX switch in the cockpit maybe faulty but most likely your have rusty AUX/BOOST Solenoid point contacts. That's why some people rap a suspected bad solenoid with a wrench to get it working.... hopefully one last time before you replace it!
Attached Files
File Type: pdf Battery Disconnect (BD) Solenoid Schematics.pdf (284.0 KB, 185 views)
File Type: pdf Bi-Directional Isolator Relay (PDF).pdf (784.8 KB, 133 views)
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Old 03-20-2017, 07:23 PM   #18
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OP stated his motorhome was a Itasca Horizon Diesel ISK40SD. Well, I went to look at the wiring diagrams and found that there is no such thing, Its an IKS40AD, KD, QD, or WD. knowing which one would help. I saw where a link was posted to wiring diagrams, possibly all models have the same wiring for this circuit.

At any rate, if the charge/boost solenoid is failed a better quality replacement would fix the problem, something like a Cole-Hersee 24213., 200 amp continuous duty, about $55 but worth every penny, silver contacts, should last a long time. Cheap ones are rated at 100 or 150 amps and simply don't hold up as well.

Charles
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Old 06-27-2017, 09:39 PM   #19
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Smile Cheaper alternative to carrying extra solenoids

While replacing both solenoids which were performing their basic functions, as most naysayers trust, what I found is this:

1) The LED lights in my coach burned brighter and so did my flourscent lights, albeit not as noticeable.

2) My engine batteries were no longer draining/bleeding out due to a short that I can now verify as being a solenoid short to ground. However, I don't know which solenoid was the culprit since I decided to replace both solenoids. (Later I will have them tested to know which one to keep.)

Note: Both the BOOST/START solenoid and the BATTERY DISCONNECT SOLENOID tested fine using a 12V test light while toggling the Battery Disconnect Switch in the entryway of the RV.

Why did I replace both? For one thing, I did not want to go to the trouble of testing for amperage. And it was easier to replace both solenoids vs. replacing just one.

Now... What about that cheaper alternative to carrying extra solenoids?

The solution came to me during this job: I strongly suggest you pickup one 12" red battery cable from Walmart, etc. The cable should have 2 flat connectors and a 3/8" hole on each end, which you can use to bypass any failed solenoid you my experience while on the road.

...Not to mention it is faster to add a jumper wire (4-gauge) vs. changing out solenoids on the road.)

This will get you home faster and/or to your repair facility too! And for only $10 you now have cheep insurance in the event one or both of your solenoids fails.

For that matter, everyone should also carry a $6 12V test lamp.

Safe travels everyone!http://www.irv2.com/forums/images/icons/icon7.gif
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Old 06-28-2017, 11:41 AM   #20
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You seem to have a need/desire to overthink/overengineer things. The easiest (and cheapest) way to bypass a failed battery solenoid is to simply remove the existing cable from one side of the solenoid and reinstall it on the other side. No need to buy/carry a short cable.
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