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Andy4639 · 10-01-2020, 11:07 AM

The floor mounted dimmer in the cab. Take the center wire loose and put your test light in the wire connector you took loose. Turn on the head lights. It should have power.
If it does your good to the dimmer, if it doesn't then the problem is in that wire some place.

If you have power plug it back to the dimmer and take one of the other connections loose and try activating the dimmer to see if it lights up. If it doesn't then your dimmer is bad. It could just be one side bad but either way you will need to change it.
If it does light up then move out to the drivers side head light and unplug it. The head lights all get 12 volts at the drivers side bulb. At least Chevy's do so I would think GMC do also. So check it first.

10-01-2020, 11:07 AM	#3
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Headlight Problems The floor mounted dimmer in the cab. Take the center wire loose and put your test light in the wire connector you took loose. Turn on the head lights. It should have power. If it does your good to the dimmer, if it doesn't then the problem is in that wire some place. If you have power plug it back to the dimmer and take one of the other connections loose and try activating the dimmer to see if it lights up. If it doesn't then your dimmer is bad. It could just be one side bad but either way you will need to change it. If it does light up then move out to the drivers side head light and unplug it. The head lights all get 12 volts at the drivers side bulb. At least Chevy's do so I would think GMC do also. So check it first. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.