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LarryDel's avatar
LarryDel
Explorer II
Jul 22, 2025

12 volt does'nt work

i have a 2022 Forest River Flagstaff 21FBRS travel trailer. In 4 years we never had an issue until now. On our last trip, our 12 volt system stopped working (fridge, slide outs, lights, etc.). I made sure that the the battery disconnect switch was on. I checked circuit breakers. All okay. Once we got to our destination and plugged into shore power, everything worked. When we got back home I had the batteries checked. They were bad, so I bought new batteries. Still no 12 volt working. So I assume the problem is somewhere between the batteries and the the inside of the trailer. By the way, I tried the electric jack using only battery power and it works just fine. But I guess that is because it is directly connected to the batteries. Any suggestions on trouble shooting before I take it back to the dealer (which charges $165 per hour).

Asking for Advice
Electric
Travel Trailer

1 Reply

  • opnspaces's avatar
    opnspaces
    Navigator III
    Jul 23, 2025

    Did you disconnect and reconnect any of the battery wires just before it failed? Is so you possibly reversed a wire and blew the reverse polarity fuse.

    You really need a meter if you want to troubleshoot this. Almost any cheap digital multimeter will work. 

    Trace the positive wire from the battery to where it enters the trailer. There is possibly a circuit breaker on that wire that is failed. If you have a meter check that there is the same voltage going into and out of the breaker. If no meter then use a short piece of wire to jump between the terminals on the circuit breaker and see if things start working.

    The 12 volt side uses fuses so check that all the fuses are good. Look online for the make and model of your power distribution center and see where the reverse polarity fuses are located and check them. 

    Here's a picture of a common circuit breaker that you might find on the tongue of the trailer.

     

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