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-   -   No 12V when on battery or alternator (http://www.irv2.com/forums/f54/no-12v-when-on-battery-or-alternator-438184.html)

Rickinnocal 04-07-2019 11:47 PM

No 12V when on battery or alternator
 
Hi,

I went to check on my RV (1990 Rexhall 29' Class A, Ford E350 chassis) on Friday, because I haven't done so in weeks and we've had a lot of rain.

On entering, I pushed the 'battery check' button to see if the house batteries were fully charged or needed a top-off, and got not even a flicker. I tried one of the overhead 12V lights, and nothing.

I was surprised, but wondered if I'd left a light on. Not even thinking, I just sat in the drivers seat and hit the button to start the genset. As I listened to it crank it suddenly hit me... it shouldn't crank if the house batteries are flat.

The genset started and I got up and checked around. No lights or anything else left on, and now the 12V and 110V systems were working fine. I turned off the genset and went outside and checked the batteries. Almost completely charged, but still no 12V anywhere inside the coach.

I started the engine, but even with the engine running I have no 12V in the coach (Other than the dash 12V outlet which is a chassis system, not coach)

So...
Genset running - 12V and 110V outlets have power.
Genset off - house batteries are charged, but no 12V in coach
Engine running - no 12V in coach

All fuses on the distribution panel are good, and all 110V breakers are set.

Any suggestions where to look first?

Thanks,
Richard

twinboat 04-08-2019 07:08 AM

Look for a battery disconnect switch.

It will cut the power to all house items.

My 1999 class C had a manual switch in the battery compartment. Some use a switch by the door that control a solenoid.

Rkesselus 04-08-2019 12:02 PM

.What twin boat said.

Rickinnocal 04-08-2019 11:36 PM

Quote:

Originally Posted by twinboat (Post 4716378)
Look for a battery disconnect switch.

It will cut the power to all house items.

My 1999 class C had a manual switch in the battery compartment. Some use a switch by the door that control a solenoid.

A battery disconnect switch I'd have known about and had to have turned off.

The issue turned out to be something I didn't know was there. There is an in-line 30A fuse in the main +12V line where it runs from the battery compartment to the grommet that brings it up into the compartment under the bed.

Silly layout! The fuse is hanging under the chassis out in the elements that come up from the rear wheels. I removed the fuse holder, spliced the ends together, taped and added a heat shrink cover. Then since the fuse itself is not a bad idea, I cut the wire just before it goes into the charger/converter and spliced in a 30A inline fuse holder.

Now everything works again, and if the fuse goes out I can do it in the bedroom, not lying under the coach.

Richard

Jkwilson1989 04-09-2019 07:55 AM

The fuse should be as close to the power source as you can get it. It primarily protects the wiring if something goes wrong along the run.

Rickinnocal 04-09-2019 11:31 PM

Quote:

Originally Posted by Jkwilson1989 (Post 4718238)
The fuse should be as close to the power source as you can get it. It primarily protects the wiring if something goes wrong along the run.

True, but which end of the wire would you consider the power source? When running off 12V it's the battery end, but when on shore or generator power and charging the batteries it's the charger end.

Since the 12V pretty much just runs the LED lighting and the stereo, there is probably more current when charging than when running off 12V, which would make the charger end the more important to protect.

Even if it isn't, I think getting the fuse in out of whatever crap the rear wheels throw up onto it is a valuable change compared to being maybe two feet further from the battery

Richard


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