120V Blowing Fuse

[Nolanb]

I have a 1984 Bigfoot 9.5 Camper I just bought. I don't know much about campers. I plugged it in to the wall and its making a humming noise and the main breaker is sticking out. I push the breaker in but it will not stay in. I pulled the (breaker unit) out of wall to look for ground wires or bare wire and did not see any. Everything works fine off of the battery. Any thoughts on what it could be?

[John in Michigan]

From what you have posted, here is how I would proceed:

(1) Since everything works OK with the 12vdc battery, I would assume the 12vdc circuits and loads/accessories are OK.

(2) Since the main breaker (assume this is the 110vac main breaker?) pops out, I would be looking for and trying to isolate a problem in the 110vac circuits. One possibility is that the main breaker itself needs to be replaced. Another possibility is that there is a problem with the 110vac-to-12vdc converter. Measure the current drawn at the main breaker. If the current drawn exceeds the main breaker rating, then you know the main breaker is OK. If the converter is the ONLY 110vac load that is turned on at that point, then I would suspect a problem with it. If the current drawn is below the main breaker rating, then the main breaker needs to be replaced.

[Gerry]

By saying sticking out do you mean tripped?
First thing I would do is to buy new breaker....
If that doesn't help you must have dead short in the 120v system somewhere.
Check the outlets and the wires going to them.

[Casita Greg]

12 VDC = Fuses
120 VAC = Circuit Breakers

It's a bit confusing from your description when you say that you are blowing fuses, but fuses are only used on the 12 volt DC side of your trailers' power distribution. If you are tripping breakers, (which are used to control the 120 Volt AC circuits, then that would be a totally different problem.) Are you having problems with 120 Volt circuits, (circuit breakers,) or are you having problems with 12 VDC circuits,(fuses?)

Anyway, the first thing I would check would be for a "Reverse Polarity" condition. That would be if someone hooked up the white and black 120 Volt wiring to the wrong terminal screws on the outlet receptacle. If you have a "Reverse Polarity" situation, this could be a problem. It would be the first thing to check for.

The next thing I would check is whether you have a short to ground in one of your AC circuits. Turn all your breakers off, hook up your shore power cord, (after making sure you don't have a reverse polarity problem in the outlet you're plugged into,) and turn them back on, one at a time, until you find the circuit that is causing your breaker(s) to "trip" off.
If it trips off as soon as you plug in, you have a definite short to ground somewhere in your incoming AC wiring, which will require physically "hand over hand" inspection of your wires and connections to find where the short is coming from.