Dome Light Problem?
 

I'm trying to figure out why the dome light in my 78 GMC isnt working. I seem to be getting voltage at the light it self,but exaclty how many volts should I be getting at the light?The entire 12 volts,or less than that?

the lamp has a constant 12V all the time. It is turned on by the door switches or light switch. These ground the circuit causing the lamp to light.

Re: Dome Light Problem?
 

uifan71, thanks for asking the question. I am having the same issue with my 78 GMC.

Re: Dome Light Problem?
 

NeCrOmAnCeR, thanks to you also for the heads-up on how this thing works. I had been looking around the net for a wiring schematic of the system but this makes it really easy to figure out.

Re: Dome Light Problem?
 

the switch might be dirty in the jam
the ground goes threw a white wire
comes into the cab with a black rubber grommet just under the dash lip at each side
some people cut the wire @ the switch or fuse panel to make the dimmer switch the only way on