Winnebago Trend holding tank heaters not working

[bigb]

There's usually a way to get wires pulled, being an electrician I have gotten pretty good at it. I pulled a data wire from my outside power compartment all the way to the cabinet under the microwave, had to pull the bottom out of the sink cabinet, remove a heat register and push the duct out of the way and get under the bed but I did it. Then I ran #8 wire to my fridge 12 volt terminal block directly from the batteries since the inadequate factory 12 gauge circuit was only supplying 11 volts to the fridge while driving, now I have 13 volts and over 40 watts more cooling power. The old circuit is still in the outside fridge compartment capped off, I could use it for something else some day. If you can get into a compartment then under the rig, and locate a switch somewhere else if it's not possible to get access to the existing location it could work. My tank heater switch is in the shower wet wall and the wires drop straight thru the floor to the heaters, accessible by removing the plumbing access cover in the shower.

[Trend_Owner]

Originally Posted by bigb

There's usually a way to get wires pulled, being an electrician I have gotten pretty good at it. I pulled a data wire from my outside power compartment all the way to the cabinet under the microwave, had to pull the bottom out of the sink cabinet, remove a heat register and push the duct out of the way and get under the bed but I did it. Then I ran #8 wire to my fridge 12 volt terminal block directly from the batteries since the inadequate factory 12 gauge circuit was only supplying 11 volts to the fridge while driving, now I have 13 volts and over 40 watts more cooling power. The old circuit is still in the outside fridge compartment capped off, I could use it for something else some day. If you can get into a compartment then under the rig, and locate a switch somewhere else if it's not possible to get access to the existing location it could work. My tank heater switch is in the shower wet wall and the wires drop straight thru the floor to the heaters, accessible by removing the plumbing access cover in the shower.

Running a new wire to the tank heating pads wouldn't be a big deal, and I would almost certainly use heavier gauge wire than Winnebago did. I could just use a fuse as a switch, or I could put a switch behind the fuse panel that I could access by pulling out the drawer above it and reaching behind the drawer to reach the switch. I would like to use the existing tank heater switch, but I don't see how I can do so without a lot of trouble.

[Morich]

What would be super nice for finding those plugs to check would be a drawing something like this but for the tank heaters.
This is for a totally different set and from 2009 but they surely have the same in their files to send you??? Knowing where the plug is hidden makes it pretty easy to find and spot if it has come apart!
Just looking for the easy way!

[Trend_Owner]

I checked the switch for the tank heater pads, and it's got good voltage going in and coming out, so I know the switch is good. The break is somewhere between the switch and where the wires come out. But they go behind a wall that wouldn't be easy to check. I don't know if there's any point in calling Winnebago for additional information, but perhaps there is. I might do so tomorrow. At this point, it's looking very likely that I'm going to need to run new wire to the heater pads.

[Morich]

I might mention something that you already have checked or not? This type plug is kind of prone to a fault that may be hard to spot if we are not really awake, so look closely at how the small pins fit in th eplug as there are times when the pins may "back off" as the plugs go together so look at each pin to see tha it is really going in and getting metal to metal contact, or test the battery and ground not just as it goes into the plug but if you can get a probe on the wire or pin as it goes out of the plug?
Sometimes using a needle to poke into the wire is handy if you can't get the probe in to touch the contacts.
Just ideas that might be better than new wires?

[Trend_Owner]

Originally Posted by Morich

I might mention something that you already have checked or not? This type plug is kind of prone to a fault that may be hard to spot if we are not really awake, so look closely at how the small pins fit in th eplug as there are times when the pins may "back off" as the plugs go together so look at each pin to see tha it is really going in and getting metal to metal contact, or test the battery and ground not just as it goes into the plug but if you can get a probe on the wire or pin as it goes out of the plug?
Sometimes using a needle to poke into the wire is handy if you can't get the probe in to touch the contacts.
Just ideas that might be better than new wires?

The plugs in the back of the switch are in there quite solidly, and I've verified that both the hot wires going to and from it have good voltage. While I can't get to the wires in the wall beneath the switch to verify that they are intact, I can get to the wires under the coach. It will take some time, but I'm going to start where they go into the coach and check their voltage. If there isn't any at that point, then I may have no choice but to run new wire. I'd like to run it to the existing switch, but running it from the switch, which is over 6' off the floor, down through the wall and the floor is probably beyond my pay grade since I don't want to take the wall apart.

[Bones2003]

Trend Owner, can you remove your monitor panel from that wall to gain a little access to the area where you might find a loose connection? It's probably not great access. Be careful if you do that because there are a lot of wiring going to the monitor panel and you don't want to cause any more problems.

Also, you can sometimes gain access from the other side of a wall through a closet or outside storage compartment. You may have to pop a panel off and could damage it a little but generally not a big problem if it is pretty much hidden anyway.

I'm not at all familiar with your RV but just trying to give you some ideas.

[Trend_Owner]

Originally Posted by Bones2003

Trend Owner, can you remove your monitor panel from that wall to gain a little access to the area where you might find a loose connection? It's probably not great access. Be careful if you do that because there are a lot of wiring going to the monitor panel and you don't want to cause any more problems.

Also, you can sometimes gain access from the other side of a wall through a closet or outside storage compartment. You may have to pop a panel off and could damage it a little but generally not a big problem if it is pretty much hidden anyway.

I'm not at all familiar with your RV but just trying to give you some ideas.

Yes, I removed the monitor panel to get access to the tank heater switch directly above it. Going underneath the coach to check the connections is my next planned step, but it's raining today and I have a busy weekend, so I'll have to delay it until next week.

[Bones2003]

I've used a cheap endoscope camera connected to my phone that I snaked into the wall through a switch opening to find wires. I did this when I replaced a light switch with a dimmer. Came in handy a few other times also in tight spots.

[bigb]

A word to the wise if you re-wire, I checked mine today and with just one tank heater and one elbow heater my voltage was only 10.3 at the pads, plugged in with converter on 10.8 but with 2nd pad heater on will no doubt drop back to 10.3 or worse. They are rated at 13.5VDC and when figuring the rated amps at the rated voltage compared to what I am getting this is a loss of almost 1/2 in terms of heating wattage. Mine are wired with AWG 12 and probably about 20 feet, in the future I plan to run 8's and try to shorten the run.
I did the same with my fridge, went from 11.2 volts to 13 volts which increased my 12 volt cooling while on the road by 44 watts or 35%.

[Trend_Owner]

I've tested the switch that is supposed to control the holding tank heating pads, and it's actually on the same circuit as the water pump. It's definitely not on the circuit marked as 'tank heater'. My guess is that it was wired incorrectly by Winnebago and the prior owner, who lived in the South, never used it and so never became aware of the problem.

Between the circuit being wired incorrectly and there being a break in the line where I cannot access it, likely under the bathroom floor, I've decided to just add a new line. It shouldn't take more than an hour or two to do it, and the only piece I need is a new rocker switch to control the circuit.

Thanks for the help everyone!

[Trend_Owner]

Originally Posted by bigb

A word to the wise if you re-wire, I checked mine today and with just one tank heater and one elbow heater my voltage was only 10.3 at the pads, plugged in with converter on 10.8 but with 2nd pad heater on will no doubt drop back to 10.3 or worse. They are rated at 13.5VDC and when figuring the rated amps at the rated voltage compared to what I am getting this is a loss of almost 1/2 in terms of heating wattage. Mine are wired with AWG 12 and probably about 20 feet, in the future I plan to run 8's and try to shorten the run.
I did the same with my fridge, went from 11.2 volts to 13 volts which increased my 12 volt cooling while on the road by 44 watts or 35%.

This calculator says that for a 12 foot run with 15 amps, which is more than enough current for the four tank heater pads we have, 14 gauge wire won't result in more than a 5% voltage drop. 8 gauge seems like overkill, and it's doggone pricy these days.

[bigb]

Originally Posted by Trend_Owner

This calculator says that for a 12 foot run with 15 amps, which is more than enough current for the four tank heater pads we have, 14 gauge wire won't result in more than a 5% voltage drop. 8 gauge seems like overkill, and it's doggone pricy these days.

I figured that out last night, the only way I could get an accurate power consumption reading with my Smartshunt was to use the batteries without being plugged in. Once I plugged in the voltage rose to 11.8 with 1 elbow and one tank pad, still almost a volt under their rating and with both pads energized will go a bit lower. I may still run 8s from the fuse box to the switch and back down to the floor under the bed just before they leave the coach, this will take care of most of the run. Then I'll add grounding jumpers to the frame. This should give me close to the full rated power of the heaters. I have plenty of #10 and #8 and even some #6 from my business that I shut down and retired from almost 2 years ago, just sitting there waiting to be used.

[Trend_Owner]

I've finally got it all done. I ran 14 gauge wire about 10 feet from the power center to the tank holding heater pads, and I reinstalled the original switch with a built-in light but moved it to the opposite wall from where it originally was. I've verified with a thermometer that all the tank heater pads are working well, and the total power draw is only 70 watts, so we can power them all night long and only use about 1/3 of our lithium battery bank's capacity. Also, I cannot detect a meaningful drop in voltage at the heater pads either, so the 14 gauge wire powering them seems to be adequate.

We're now prepared for sub-freezing temperatures! Thanks again for the help everyone!