no power inside my 1994 Fleetwood Tioga class C

The voltage on the battery and the breaker read 12.7, there is no corrosion on the terminals and all the screws are tight. There is a small amount of electricity going inside the RV it only powers the water pump, heater and the LP gas detector.

I have the same vehicle. I thought Jim Shoe nailed it. Under the hood, under the solenoid that isolates the batteries is a small blade type fuse. Pull it out and check it.

What voltage readings are you getting at your batteries? Are you getting the same readings at your battery soliniod? Are you getting the same readings at the 12 v fuse panel? The two things I would look at first if you are sure the polarity is correct is the cable connection to the inside of the terminals look for green corrosion or loose terminals. Also I found the set screws at the 12v fuse panel can sometimes loosen and need to be tighten.

Thank you to all my RV enthusiasts I have looked at all the suggestions you have provided me I'm still at square one. the only thing i have left to do is to test the amps on the battery and the circuit breaker but if there ar any other suggestions I welcome them all.

You should have an auto-reset circuit breaker in the engine compartment on the cable that goes back to the converter from the house battery. You should be able to read 12V on both of the terminals. If not it could have failed.

Circuit Breaker

I have the same exact unit. I keep my mine inside a building with 30AMP wiring installed. I unplugged it from the wall outlet one time but forgot to plug it into the outlet in the power/cable compartment. Nothing worked on the inside. When I plugged it into the compartment, everything worked. I blame it on "brain fade". That's the easiest thing to check first.

Do you have a volt meter or a 12v test light? Check for voltage at the battery and follow the wiring to see where you loose the voltage. Sure sounds like the polarity is reversed, but maybe a fuse, circuit breaker, or a corroded connection.

My house battery has also 1 negative cable to the negative an 1 to the positive. Prior to replacing my batteries I did have power inside . When I replaced the soleinoid I installed tha cables just as i took them off one at a time and to the right connection.

Your 12VDC Converter/Charger is being supplied by the 120VAC from Shore Tie or Generator. When it doesn't have that 120VAC, it isn't connecting your battery to the 12VDC outlets. I hope it's not because you got the polarity reversed, which isn't all that hard to do. Our Jayco has only one Negative Cable to the House Battery, but FOUR to the Positive of the Battery. A couple of those were corroded and not making contact. It'd also be easy to leave one or two of the four off. I taped the four together to form a bundle. The terminals still have to be put on the battery post, but at least I keep them where I can find them all.