12v lights

[RichTownCa]

I have a 79 Fleetwood pace arrow with a Dodge chassis have no running or brake lights and all fuses are good brake light switch is good bulbs good don't know if the living area 12v lights have anything to do with the running or brake lights the 12v light above the couch and above the table stopped working I put a volt meter to the wires the meter showed 12v left the meter hook to the wires and plugged in a bulb when I did that the meter went from 12v to 0v bulb did not light up can someone tell me what to look for and how to go about fixing this issue Thanks

[ScottG]

Verify the ground connection at the tail lights.

[MEXICOWANDERER]

Checking lamp sockets with a meter is useless - use a test light probe with alligator clip to ground. You may need a length of wire i.side to reach a guaranteed good chassis negative --.

Many of the older rigs had wire access only behind one tail light or another. You.have to remove the housing.

No connection whatsoever between outside tail lights and inside house lights.

But first you need to put a load on the circuit by using a light bulb. This testing problem is as old as the hills.