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Old 07-05-2004, 09:50 PM   #1
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Question No 12V Coach Power

This happened on our last trip but I'm just getting to it now and I'm a little puzzled.

The 12V coach power is not working unless:

1. The coach is plugged into shore power
2. The genset is running (same as above)
3. The 12V Chassis system is on (engine running).

Otherwise no power for lights, etc.

Any ideas where to start? I have 12V at the batteries. I've been suspicious of the batteries for a while now...but this just kinda happened. Like a fuse but nothing looks blown.

All advice welcome.
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Old 07-06-2004, 06:09 AM   #2
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try this..

Quote:
Originally Posted by swebster@myrvadvanta
This happened on our last trip but I'm just getting to it now and I'm a little puzzled.
The 12V coach power is not working unless:
1. The coach is plugged into shore power
2. The genset is running (same as above)
3. The 12V Chassis system is on (engine running).
Otherwise no power for lights, etc.
Any ideas where to start? I have 12V at the batteries. I've been suspicious of the batteries for a while now...but this just kinda happened. Like a fuse but nothing looks blown.
All advice welcome.
swebster,
I'll just try to cover a few basic points:
If you have a good digital volt-meter, try measuring for 12v at one of the 12v fuse on the power panel. This will quickly tell you if it's a fuse or not.
Corrosion between the fuse, and the fuse-holder could be checked as well. Easy to clean if present. This should tell you also what condition the 12v system is at.
Another thought, if all of the above is good and, you still don't have 12v to your lights, frig, etc., then I might suspect a loose wiring somewhere.
The way these 12v system are wired, 12v is supplied to all of the outlets continuously, with each having it's own independent switching. If you have loose connection in the 12v line, then it's very possible nothing is going to work.
Good luck~
ciao
53FC
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Old 07-06-2004, 06:22 AM   #3
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Quote:
Originally Posted by swebster@myrvadvanta
.......Otherwise no power for lights, etc.
Any ideas where to start? I have 12V at the batteries. I've been suspicious of the batteries for a while now...but this just kinda happened. Like a fuse but nothing looks blown. All advice welcome.
Steven:

Did you check the voltage at the clamped battery terminal or on the post itself?

Sure is strange that you have NO lights at all - you would expect some lights to be working, although very dim, if it was a battery problem....therefore I would suspect the wiring.....first the battery terminals....terminal to post contacts are always a good place to look for hidden corrosion.

Next, I would check the contacts and operation of the "Battery Isolation Switch" mounted on the back of the battery drawer....might have an internal problem or a bad connection or terminal on the back - this would be a good opportunity to clean the connections. From the Battery Isolation Switch, my main wiring goes to a frame mounted safety breaker. It is mounted on the outboard face of the curbside frame, about the middle of the battery box.

I believe (but not positive....don't remember for sure....) that the "cometogether" point of all three coach electrical systems (Univolt, Alternator charge line, and Coach Batteries) is the upstream side of the above referenced breaker.

Please post what you find on your 345.
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Old 08-03-2004, 03:24 PM   #4
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Well this is fun... I'm not here with any answers. I'm here to make it harder. I have almost the exact same problem...one main difference is that I found this out just this afternoon and have not had time to dig into it too much. I JUST bought this 1974 Argosy MH.
The things I do know:
- When I got it home the lights inside worked fine when nothing was running or plugged in (They seemed more happy when the Gen. was running).
- There are 2 batteries in the front compartment under the Passenger.
- There appears to be battery connections in the rear for the same/similar batteries...but there are no batteries connected.
- On the drivers side there is a panel that has in it a blue box that says "Airstream battery charger and power supply"
- Next to that there is a much newer looking battery charger with a meter on the face.

I plugged the whole thing into AC power to test the fridge and to save my batteries while I was playing with lights and such. I figured that the battery charger would kick on and begin to work on the batteries (it is bolted down and wired in). When I plugged in all I got was a healthy hum from the big blue box. The battery charger just sat there lifelessly. Everything in the cab still worked, now they were nice and bright. I left it plugged in over night and the next morning the fridge was cold and everything was still working fine. Last night I went in it and had several lights on...all were nice and bright, my battery check switch showed "good". This afternoon on my lunchbreak I came home and my wife had unplugged the MH so she could vacuum. I thought "the batteries have charged for a day and a half I'll see what the batt. check says". I checked, nothing. lights? Nothing. But it still starts up just fine. I plugged it back in and everything seemed back to normal. so basically nothing works unless either the Gen. is running or I'm getting AC from a wall. like I said I have not done any homework on this so I really do not know more than that...but the symptoms sound similar. And I don't know about that batt. charger and the extra batt. cables in the rear.


AGHHH! I love it! haha!
-Logan

p.s. thanks again for all the help I've already recieved!!!
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Old 08-03-2004, 03:38 PM   #5
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Since you have a custom job I am going to have to guess on a few things.


The batteries under the hood on the pass side originally were 1 for engine 1 for coach. Check here first, you may just have a dead one

It sounds like they made them both for coach. Not really a problem since they are a royal PIA to get to to check water, etc.

The battery connections in the rear are likely for the coach batteries. If they made room for 2 it is a define upgrade. While you were plugged into shore power the blue charger was powering all of the 12 volt systems in the coach. The older univolt could do this without a battery. Once you unplugged the lights no longer worked due to a lack of a battery.

The secondary battery charger may be for the engine batteries. Many of these coaches have parasitic drains that kill the starting battery over time. This would address that issue.

So my suggestion tis to measure the space for the coach batteries and visit your local battery man. 1 is good 2 are better. Try to get them from the same lot if possible, matched batteries will last longer.
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Old 08-03-2004, 04:07 PM   #6
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I don't know much about 12V electrical systems in trailers but in cars , if the battery is good and a fuse hasn't blown and you have no power at all, it's probably a bad ground. It seems to me if the 12V systems works with the generator or shore power, you've isolated it to the battery and if the batteries are good maybe you just have a loose ground wire. Check the continuity.
Jack
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