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Old 10-10-2023, 01:08 PM   #1
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2001 Itasca Suncruiser 35U owner needing help

If anyone has any information I could use to find help with our 12v system I would appreciate it. Everything has gone crazy. We have no 12 volt power at all to the point that my cigarette lighter (I use it to power my Garmin) doesn't work and I can't start the generator. When I am plugged in to AC everything is fine. I have bought new house and engine batteries and replaced the Aux switch on the wall coming up the steps and still zilch. I'm just learning to navigate my way around the forums so please be patient. Thanks for your help.
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Old 10-10-2023, 02:54 PM   #2
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OK! Sounds like new user and that often means extreme confusion. I don't want to seem to talk down to you but there are some basics that we can get straight to make sure we are talking on the right level and all are speaking the same language!!
Easier to avoid lots of confusion if we can get the confusion out of the way upfront. no offense intended if you already know some of this stuff?

I like to thing of the RV as having three sets of electrical stuff that connect at times and places and disconnect at other times. That can make it really seem too much to handle, so I like to look at each set alone and then we can talk about how they connect.

Easier for many to understand is the part lots of us know from using cars or trucks.
That 12VDC part is the same as a normal truck. Chassis battery starts the engine that has an alternator that charges that battery and also runs headlights, wipers, and outside clearance lights like a truck would. Also there is often a 12v outlet on the dash like a truck might have!

So if the truck won't crank and start, it is in the normal wiring that a truck has! Chassis battery has to be good, cables from ground to that battery good and cables from battery to starter solenoid have to be good. Just like a truck, because the RV is built on a truck chassis that they buy from whoever builds it and lots of the parts are already there, so we need to search and look for what is wrong with the truck!
Sometimes the parts are hidden or there are some RV which have a chassis battery disconnect switch that has to be on. Some do, most don't, so don't worry if not found!

There is also the coach 12VDC system that has the coach batteries and powers most of the inside things like inside lights, fans and water pump, etc. It gets power from a converter/charger that takes AC power from the cord or generator and makes 12volt DC. The generator starts off the coach batteries and many of the controls for air and furnace also use the coach 12Volt.

Third system is the 110 AC from the cord or generator that makes the converter work and also feeds power to the 110 house type outlets and big power users like the microwave and air conditioners.

I would suggest looking at the "normal" truck group first as the far more simple one that we may know some about already?
Sometimes getting one working also makes the other work, too!

To get a truck to start, we have to have a good connection from the ground to the charged up new battery and on to the solenoid (switch?) Good clean connections of both positive and negative posts?

Then a cable has to take the power to the solenoid on the side of the starter.
When we turn the key, the solenoid closes contacts that put power to the starter to turn it.

Do you mean you can crank and start the engine when RV is plugged into power? That would seem the AC power makes the 12VDC going to the coach batteries and that power gets passed to the chassis to start the engine!
This is a normal connection that is made when we turn the key and it connects the two groups together to let the alternator recharge the coach batteries as we drive! But it can confuse the heck out of us until we know that, right?

Since the batteries just had work, I'm guessing the cables on them are not quite right or making good connections.
Since the coach 12V is a problem too, I might look at the cable from the negative posts to the ground and be sure it is clean and connected well.

My basic idea is that the batteries do not work because they have no ground but when power comes from the cord, the converter is "making" power to do things!

Click these snips to get a better look at why I think both coach and chassis batteries have the same problem and may use the same point to get that ground!

Chassis drawing of battery
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Coach drawing of coach battery
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When the cable I marked with red slash is open, neither battery will work and they both go to the same place, so look that over carefully and see if it makes sense.

Let us know what you find and if my guess is wrong, we can go in other directions. Just looking for the first guess, at times?
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!
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Old 10-10-2023, 02:54 PM   #3
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Greetings DBHutchins,
Is it possible that a fusible link coming out of the house batteries has failed? I would take a multimeter and start checking voltages from the batteries on-out.
Welcome to the forum.
2019 Minnie Winnie 22M on an E-450 frame
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Old 10-10-2023, 06:14 PM   #4
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Morich, thanks for responding. The motor cranks perfectly all is well with the chassis side, however we have to be plugged into electrical for anything else to work. One thing I can't do is turn on the generator when the engine is running or when it's not. Any thoughts on that?
Happy Camper
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Old 10-10-2023, 08:15 PM   #5
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That narrows it down a bunch and the big thing is that the generator cranks off the coach batteries!
A couple points to check.
One is that the mode solenoid is controlled by a small wire just as drawn in the pictures above. That wire should get 12volts on it at two times. One is when we are pushing a switch near the drivers, often labeled different ways. Maybe Aux, boost, etc and it closes the solenoid to do a "jump start using the coach batteries to boost a weak chassis battery!
The other use for the small LR wire is to close the solenoid when the ignition is hot like when the engine is running.
If all is right with the solenoid and the engine is running this solenoid should be connecting both batteries together to let the generator crank.
If you have the coach battery disconnect open, that opens the path from the coach bat to most everything else inside like lights and also the generator starter!

Kick it around a bit and let us know what you find? Good luck as it's got to be a stress!

Maybe do this check first as much easier to find the switch and make sure it is right and closed to make all the inside work as well as generator crank.
That relay being left open should kill just about all the RV stuff except it leaves safety items like propane and CO detectors working.
They don't want to blow you up without getting an alarm first!!

A couple things to check are that the solenoid is closing and we can often hear it "thump" if the area is quiet or we are close to it. If you can get a hand on it, you can often feel it move! That doesn't always mean the contacts inside are good and passing the power on through, though. They can get burned or corroded!
One way to make sure the power from chassis is getting to the coach batteries is to put a jumper cable between a positive post of the coach to any positive post of the chassis battery.
Do you have a jumper cable onboard and are the two battery sets close enough together to do that?
If you connect them together, have the engine started or running and then try to crank the generator, that is one way to tell if the problem is the solenoid not working right to connect them!

Have you spotted a label about solenoid and battery disconnect relay? Maybe near the outside back on driver's side?
This drawing is what they should look like and they draw it pretty close to what you see! Solenoid is silver metal can on most and relay is to the right and black plastic looking thing?
Click this snip to get best view!
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Big lug on left of silver can is chassis battery cable. I drew it red. Small wire in middle is LR that makes it wove and on right is big cable from coach batteries. When contacts close both are connected together!
Then the green marked line goes out the right side to the coach battery disconnect relay. There should be a switch inside to turn this relay on/off or engage/disengage. the relay closing puts the power on through to the right side with wires going to most of the RV stuff, lights, fans, pump! Also power goes to the generator starter!

Make sure to push the disconnect switch inside toward the engage side and check if the lights inside start to work. If the inside works, then the generator should also have power to crank!
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!
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Old 10-10-2023, 08:43 PM   #6
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Found a couple things if you are not up on them?
Boost switch to control solenoid and battery disconnect switch near door.
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Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!
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Old 10-12-2023, 08:02 AM   #7
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Location: Bolingbrook, IL
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If it's like my 2000 35U, check the 12 volt 40 amp breaker behind the panel at the top entry step..
KC9NPT (Merrill)
2000 Itasca Suncruiser 35U
2014 Chev Equinox LT AWD
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itasca, suncruiser

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