1975 Tioga wiring issues

[porter481]

Interior lights do not work unless a separate ground wire is connected to them from negative post on auxiliary battery to the bulb socket. When connecting a ground to a single ceiling light fixture all lights work.

I have also checked the all fuses I can find in the power converter and the 2 fuse boxes under drivers side near brake/ gas pedal area.

There is 12 volts DC power from auxiliary battery to the converter. All fuses have been replaced. Even when plugging in the shore power there is no 12 volt DC power to anything as well.

Also water pump is not powering up due to no positive power, but does have a negative grounding.

Is there a main ground connection for all of these light fixtures? I am stumped and have looked everywhere.

[Hclarkx]

Originally Posted by porter481

Interior lights do not work unless a separate ground wire is connected to them from negative post on auxiliary battery to the bulb socket. When connecting a ground to a single ceiling light fixture all lights work.

I have also checked the all fuses I can find in the power converter and the 2 fuse boxes under drivers side near brake/ gas pedal area.

There is 12 volts DC power from auxiliary battery to the converter. All fuses have been replaced. Even when plugging in the shore power there is no 12 volt DC power to anything as well.

Also water pump is not powering up due to no positive power, but does have a negative grounding.

Is there a main ground connection for all of these light fixtures? I am stumped and have looked everywhere.

Interesting problem. But, you are on the right track. It seems there's an open connection or broken wire between the negative post of the battery and your 12 volt lights and other devices. The water pump is seeing a ground so the break is not right at the battery. I.e., some things (water pump) are seeing ground but others are not.

Hopefully the break is in the vicinity of the battery where it's accessible. With a 46 year old RV, you could be looking at a screw terminal or some connector that looks good, but is actually an open circuit (due to corrosion). Start wiggling things and tightening screws and such. If nothing near the battery helps, look around the 12V fuse panel. There is likely some kind of common ground there where the ground for lights and such come together, maybe to a ground strip. That ground strip should be connected to the battery with a sizeable wire. Look for problems between that ground strip and the battery.

The water pump having a ground but no hot lead is likely a different problem. Unless the wire colors are fooling you and it's the water pump ground that is open. That would suggest a problem in the ground wires closer to the battery. If the water pump positive wire is not "hot" when the water pump switch is on, you need to trace that circuit from the water pump to the switch and to the battery (and maybe a self-resetting circuit breaker near the battery if not a fuse in the 12V fuse panel).

Good luck.