12 volt problems

Roy, there is no inline fuse in open site. There must be one in the wire loom. Tomorrow when it is day light, I will unscrew the wire loom from the frame and look in it for a fuse. I did find a harness inside where the wires come in through the floor. There are no volts coming from the battery. This harness is about 5 feet from the battery, so that should make it easier for me to trace.

Pitch the harness I found is actually a housing where an extra plug snaps in. There is nothing in the box. I guess it is for adding maybe an extra battery plug or something to that affect.

PITCH - I wouldn't mind if you would take over here. I did becaUse it didn't look like he was getting anything answered. I'm probably TOO LONG WINDED to really help him haha...

With bunches of us all hitting him with different things to check is probably really confusing him big time...

I was thinking maybe one thing at a time until he answers back then go to the next item to check???

Roy Ken

Go to the plug you found on the frame. Open it up,inside will be a 30A blade fuse. Pull it out and check it. Have you used the 12v system since the battery was installed?

I guess we can start at the battery itself and find the POSITIVE TERMINAL (+) and look for an IN-LINE ATC FUSE HOLDER.

It will look something like this...


This ATC FUSE will be a LARGE SIZE rating fuse. It usually is right next to the battery but may be just under the frame or maybe inside a electrical junction box mounted to the frame. This FUSE is suppose to blow to protect your battery wiring in case of a DEAD SHORT on the main battery cable.

You want to try to find this first then we will locate the other TWO FUSES mounted on your 12VDC Power Distribution Panel where your converter/charger is located.

One way to test this is to measure your battery voltage without the shore power being connected. If your battery is fully charged then your VOLTMETER will read 12.6 or so DC VOLTAGE. When you connect the shore power cable this 12.6VDC should increase to 13.6VDC if it is connected all the way to the converter/charger chassis.

The other way to test it is to disconnect the positive terminal battery lead and see if you read the 13.6VDC when the converter/charger is running when shore power is connected. The down side of disconnecting the battery cables is you might spark it against something and that will blow fuses. Its best to measure thing all connected up.

Since you already know your ceiling lights don't come on without shore power connected this is telling you the battery 12.6 VDC is "NOT" making it back to the 12VDC Power Distribution Panel. You need to start tracing connection I guess to see where the 12.6VDC is not being read with your DC VOLTMETER. the first thing is should see is the IN-LINE FUSE we are looking for... If you find the ATC fuse holder shown above then you will need to pullout the ATC fuse and see if it is blown or not...

Roy Ken

RoyB wrote:
usually when this question comes up it is related with the accidental sparking of the battery cables which end up blowing an in-line fuse close to the battery install area. Sometimes the battery cables get reversed and this also blows the same in-line fuse along with two fuses in the 12VDc Power Distribution panel labeled REVERSE POLARITY.

Find these THREE FUSEES and check out.

The DC OUTPUT of the Converter/Charger unit goes directly to the Battery thru these three fuses... i.e. both the converter/charger unit and the installed battery both provide 12VDC to power the 12VDC Power Distribution Panel. A quick check is your ceiling lights. They are 12VDC lights and if all is connected will work when on SHORE POWER or BATTERY by itself.

Some installs may have a BATTERY DISCONNECT in this same line as well... This could be a manual switch or a SOLENOID type relay.

Roy Ken

Roy all the lights work when plugged into shore power, none work when on the battery itself.

Let me see if I can answer all of these. First I have no clue what the coach side means. I have 12 volts when plugged into the house, 0 volts when it is not. I bought my TT last September from Camping World. They installed a new battery when I bought it. Where might I find these 3 fuses. Now I have been digging and I noticed the plug coming from the battery at the tongue is plugged into a harness, but there appears to be no wires going to the harness. I took a pic, but I can't figure out how to attach the pic.

usually when this question comes up it is related with the accidental sparking of the battery cables which end up blowing an in-line fuse close to the battery install area. Sometimes the battery cables get reversed and this also blows the same in-line fuse along with two fuses in the 12VDc Power Distribution panel labeled REVERSE POLARITY.

Find these THREE FUSEES and check out.

The DC OUTPUT of the Converter/Charger unit goes directly to the Battery thru these three fuses... i.e. both the converter/charger unit and the installed battery both provide 12VDC to power the 12VDC Power Distribution Panel. A quick check is your ceiling lights. They are 12VDC lights and if all is connected will work when on SHORE POWER or BATTERY by itself.

Some installs may have a BATTERY DISCONNECT in this same line as well... This could be a manual switch or a SOLENOID type relay.

Roy Ken

darlingtontrio wrote:
Hopefully someone can tell me what to check. When I unplug 110 volt from my TT, I get nothing working at all. I have checked the battery and it has 13 volts. The battery is also plugged into the wiring harness on the tongue. I grabbed my volt meter and when the TT is plugged into 110, the low voltage breaker is working. The power inverter is also working, the light and the fan are working on the power inverter. When I unplug the power inverter, everything dies, which I assume it should. When I pull the 110 power, the low voltage breaker reads 0 volts. Where should I look to figure out why I am not getting any 12 volt power. I am sure there is something, but I am new and not sure where to start. Thanks in advance.

first, it's a power converter, not inverter. inverter is a different animal.
second, did you recently remover or replace the battery?
many times, owners accidentally cross the battery wires, triggering the resettable fuse/breaker that's located along the A-frame of the trailer. they are usually gray or silver and have a tiny black button you need to push, to reset it.

Converter, not inverter.

I think I know what a low voltage breaker is. If there's 0 volts on the coach side, and 12v on the battery side, there's your problem.

What is the coach-side voltage reading when it's plugged in?