Electrial issues

Recently purchased an 1985 Pace Arrow 34'(44k mileage). It needs some work but is overall worth it.

I have a couple questions pertaining to electrical.

While on shore power everything (electrical) seems to work fine. When I disconnect the shore power all the house lights go out. I replaced all three batteries (one engine, two house) but still no lights from the batteries. When I turn on the key to the start (no engine running) the lights will come on. When I start the engine the lights will stay on. But when I shut down the engine (key off) the lights go out again.

I thought that I had the wires on the batteries incorrect but there is no change when I switch the wires around. I disconnected the 'engine battery' (engine off) and the lights went out. So I don't know why the 'house batteries' are not powering up the house.

It has a AC/DC inverter/breaker box in the back bed room (which will be my next exploration), and I can not find the switch/relay (that everyone is talking about) that controls the power from the different sources.

Can someone help me find the switch that is energizing the house lights while the engine is on :question:


Senior Member
Electrial issues

It is possible that there is an ignition cut out installed in the unit which cuts the house power when the key is off (either for security or because it was draining the batteries too fast). Can you find the fuze box for the 12v house circuits? If so, check to see if you have 12v at the input to the fuzes with the key on (you should or the lights wouldn't work at all). Now turn the key off. If the power goes away, then you need to trace the wires from that point badk to the batteries, looking for the relay or other device which is interrupting the power.

The 'switch/relay (that everyone is talking about) is the 'transfer switch'. It selects between 120V sources, and if you don't have/never had a generator, you probably don't have one. Since your problem is with 12v, it probably is not involved even if you do have one. To find it, trace the power cord to find a featureless box with 2 120 sources coming in, and one going out to the AC breaker box.
Electrial issues

Thanks for your response,

I will be looking to see if the converter swtich is my problem. The previous owner lived in the motorhome for many years only on shore power. I am thinking that the switch is seazed to the shore power side. I have to find that switch.

The house lights work when I run the engine (or just turn the key to 'on') and as I understand the shore power / house battery switch is seperate. I got to find it to check it.


Senior Member
Electrial issues


Are you still looking for help? If so, it is quite normal for the lights to work as you say if there is not coach battery installed. It may well have a battery isolator that shuts off the coach batteries as that is a very common accessory. If it does, there should be a control switch for it somewhere. The most common place for such switches is on the dash or near the entry door. If it is there, there will also be a large relay or solenoid in the main power line if you trace the positive lead from the coach batteries. There will also be one that connects the chassis 12V system to the coach batteries to charge them and to supply 12V power to the coach. That is clearly working since the lights work with the engine running. The fact that everything works when on shore power means that your 120V/12V converter is working fine. So that leaves the problem of the battery. In most RVs of the age you have the converter is not one of the type that has a transfer relay but it ties directly to the coach 12V system. The only way to know for sure is to trace the positive cable from the coach battery.
Electrial issues

Just to let you all know I found the problem with my house battery power, and it turned out to be one of those DUUOOOOPPPPEEE!!! moments.

The previous owner had placed the house battery input line on the fuse box. When I figured out which wire went where the house batteries worked.

Thanks to all for your assistence :laugh: