Hi guys, have not posted here in several years as I have been working out of country. The trailer also has been sitting, but I have tried to keep it In working order. However I have discovered a problem that maybe you guys can help me with. I seem to be having problems with the electrical system. When plugged into shore power (110v) everything works fine. Unplug from 110 and nothing works (lights, bathroom fan, etc) even though I have installed a brand new battery. If trailer is plugged into truck, everything works fine including tail lights. I have checked electrical panel and everything seems fine, no loose wires or blown fuses. Has anyone experienced this type of problem. Any ideas to fix this. Thanks for the help. Greg

Look on the tongue of the rig for a circuit breaker. They are sometimes hidden in the metal junction box where the trailer umbilical cord changes to trailer wiring.

I'm confused by your statement If trailer is plugged into truck, everything works fine including tail lights. Truck doesn't provide any power to trailer (lights, bathroom fan, etc). It only provides a 'charge' to the trailer battery which then supplies the DC power to dist. panel.If you installed new battery and connected the cables backwards you would have blown the 'reverse polarity' fuses on the converter and get no power from battery.If the DC circuit breaker on positive cable from battery to converter was tripped/not reset you'd get no power from batteryIf new battery voltage was low...truck charge line might have supplied enough DC voltage for items to work.....but usually that charge line size prevents much of a dc load. Typically takes hours of drive time to recharge a semi-low battery.:H

Third post probably has it correct. The 12 volt from the truck usually connects to the load side of the breaker on the tongue of the trailer. If that fuse is open you will have power when connected to the truck and when plugged in to a. Battery will have two wires on positive, one for break away switch and a heavier one to the fuse. Look for something with two terminals and a rubber cover on the trailer tongue. If you can use a volt meter it is easy to spot. Less likely, but possible, is you are missing a connection to the new battery. Do you have a heavier wire near the battery disconnected?

12 volt not working | Good Sam Community

11 Replies

opnspaces
Navigator III
Jun 27, 2014
Got to love a simple fix. But I would go one further just to make sure. I would unplug shore power and measure your battery voltage. then plug back in and measure battery voltage again. You should see an increase in voltage if you're charging.
DiskDoctr
Explorer
Jun 27, 2014
I love a happy ending :)
Windsor_Wilsonz
Explorer
Jun 27, 2014
Well I figured it out and feel a little stupid. I checked the electrical box mounted to frame just behind battery and everything seemed good. I measured voltage and was good at battery. Went to circuit panel/ power converter and measured only 3.8 volts coming from battery. Went back to battery and disconnected the two cables only to discover a very minor amount of corrosion on the cable ends. I cleaned them up with wire brush, reattached to battery and now everything works fine.
In the end I over looked something simple and easy to fix. I learned my lesson. To everyone who offered their help....thank you. Greg
enblethen
Nomad
Jun 27, 2014
Some do not have a rest. They just rust and fall apart!
Non-metallic ones are a little better, but any should be protected from hostile environment.
bikendan
Explorer
Jun 27, 2014
Windsor Wilsonz wrote:
Thanks guys. I will try and dig further into what is causing this issue. I don't ever remember seeing a fuse on the a- frame. I will look closer. Again thanks.

should look something like this:

you push the tiny black button to reset the breaker.
Windsor_Wilsonz
Explorer
Jun 27, 2014
Thanks guys. I will try and dig further into what is causing this issue. I don't ever remember seeing a fuse on the a- frame. I will look closer. Again thanks.
AllegroD
Nomad
Jun 26, 2014
Have you tested the batteries?
Sea_scape
Explorer
Jun 25, 2014
Third post probably has it correct. The 12 volt from the truck usually connects to the load side of the breaker on the tongue of the trailer. If that fuse is open you will have power when connected to the truck and when plugged in to a.

Battery will have two wires on positive, one for break away switch and a heavier one to the fuse. Look for something with two terminals and a rubber cover on the trailer tongue. If you can use a volt meter it is easy to spot.

Less likely, but possible, is you are missing a connection to the new battery. Do you have a heavier wire near the battery disconnected?
Old-Biscuit
Explorer III
Jun 25, 2014
I'm confused by your statement

If trailer is plugged into truck, everything works fine including tail lights.

Truck doesn't provide any power to trailer (lights, bathroom fan, etc). It only provides a 'charge' to the trailer battery which then supplies the DC power to dist. panel.

If you installed new battery and connected the cables backwards you would have blown the 'reverse polarity' fuses on the converter and get no power from battery.

If the DC circuit breaker on positive cable from battery to converter was tripped/not reset you'd get no power from battery

If new battery voltage was low...truck charge line might have supplied enough DC voltage for items to work.....but usually that charge line size prevents much of a dc load. Typically takes hours of drive time to recharge a semi-low battery.

:H
enblethen
Nomad
Jun 25, 2014
Look on the tongue of the rig for a circuit breaker. They are sometimes hidden in the metal junction box where the trailer umbilical cord changes to trailer wiring.