12 Volt Power Issues

The other day, I went by to do some routine maintenance and exercise the generator and on entering the coach, I heard a faint continuous squeeling noise.  I couldn't tell where it was coming from.  I tried starting the generator, but it wouldn't turn over at all.  I'm still not familiar with the 12v/110v systems in an RV but I assumed it was a dead house battery.  I also had noticed that the battery disconnect switch located on the left side of the steps didn't seem to work when I switched it On or Off.


My first step was to take a look at the wiring diagram that Winnebago website provides online and I found the one specific to my 2000 Adventurer 35U and saw there were solenoids that control the 12 volt power coming off the battery.

Well, first things first, I checked the battery terminals on both the house and chassis batteries.  They were clean, but not tight enough, so I cinched them down and still no 12 volt power to the coach and generator wouldn't start.  I had no trouble cranking the engine and the alternator provided enough power and the generator finally started.  Bingo, I had 12 volt power restored and I realized there must be a 110v/12v converter onboard, still have not taken the time to locate it yet.  To test my theory that the battery disconnect solenoid was the problem here, I shut down the generator and the 12 volt system went out, that confirmed there was a converter that provides 12 volt power when the generator is running or on shore power.  That's when I discovered where the continuous squeeling noise was coming from.  There is a 12v/120v inverter mounted in the cabinet above the passenger side seat that's used to power the TV...it was left on and ran down the house battery.

Before I removed the panel where the solenoids were, I checked the voltage of the batteries will all systems off and they read 12.5 volts.  I started the engine and checked again and they read 13.8 volts indicating the alternator was charging both batteries.

Now it was time to take a look at the solenoids that are hidden behind the 12 volt breaker panel and I noticed the main 40amp breaker was popped.  I reset it and BINGO, I had 12 volt power to the coach again.  Investigating further, I inspected both solenoids and saw an automotive fuse on the left side of the disconnect solenoid, it was blown too.  A quick replacement, and BINGO, the battery disconnect switch worked and I am now able to disconnect the battery when my RV is in storage.

See my comments below on the wiring diagram for the location of the fuse I replaced.  I plan on keeping some spares onboard in case this happens again.

Here's a good link to information about RV 12 volt systems:

http://www.marxrv.com/12volt/12volt.htm