88 GMC wiring/lighting

Deetz33 · 06-03-2009, 01:20 PM

I have a 88 GMC 2500 5.7 350... anyway I'm having problems with the rear lighting. When driving the truck during the day turn signals and brake lights work fine, but when i hit the light switch to turn headlights and rear running lights on, no! lights in the rear work. The headlights still work but no lights in rear work i replaced all bulbs in back, no help i have power going to the sockets so I'm wondering if it's a bad ground or bad reley somewhere in the wiring I dont really know where to start looking so if someone could point me in the right driection that would be a great help thanx.

scavanger · 06-03-2009, 06:14 PM

I think your right ,, grounds. Make sure your headlight and marker light grounds are good in the front. The back are grounded to the body, not too good of a plan with a pickup. Attatch a ground from box to frame and then make sure your sockets are well grounded. I had one truck that had problems with the wires above the exhaust system in the frame, some of the insulation was gone.

Scav.

cburcham73 · 06-04-2009, 04:18 AM

check your headlight swith also. i had the same exact thing on my 85.

06-03-2009, 01:20 PM	#1
Deetz33 Junior Member Join Date: Jun 2009 Location: Dundee, OR Posts: 1	88 GMC wiring/lighting I have a 88 GMC 2500 5.7 350... anyway I'm having problems with the rear lighting. When driving the truck during the day turn signals and brake lights work fine, but when i hit the light switch to turn headlights and rear running lights on, no! lights in the rear work. The headlights still work but no lights in rear work i replaced all bulbs in back, no help i have power going to the sockets so I'm wondering if it's a bad ground or bad reley somewhere in the wiring I dont really know where to start looking so if someone could point me in the right driection that would be a great help thanx.

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06-03-2009, 06:14 PM	#2
scavanger Senior Member Join Date: May 2007 Posts: 394	I think your right ,, grounds. Make sure your headlight and marker light grounds are good in the front. The back are grounded to the body, not too good of a plan with a pickup. Attatch a ground from box to frame and then make sure your sockets are well grounded. I had one truck that had problems with the wires above the exhaust system in the frame, some of the insulation was gone. Scav.

06-04-2009, 04:18 AM	#3
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 198	check your headlight swith also. i had the same exact thing on my 85.