rear lights - The 1947 - Present Chevrolet & GMC Truck Message Board Network

slowboy · 03-23-2021, 06:11 PM

I removed my bed on my '72 GMC to have rockers and cab corners replaced. I had 2 aftermarket brake/turn lights strapped to the rear chassis so I could drive truck. I removed aftermarket lights, put my bed back on, connected harness to rear lights. Now the only lights working are the turn signal lights. The brake, park, and backup lights don't work.

I've searched this forum but not sure what to do except make sure all lights are grounded to frame.

I don't see a black ground wire from harness. There 'is' a brown wire from harness that's sticking out by itself. I tried grounding it to frame but that didn't help. Then I saw in Haynes book that that was the wire for License plate light.

Please help...

Thanks,
Keith

**Ironangel** · 03-23-2021, 06:31 PM

The bed needs to be grounded to the frame...Battery ground to motor, motor to cab, cab to frame and bed to frame. I add extra ground straps on both sides of the bed and cab and I also run a ground from battery to frame as well...When a light starts acting up try using a jumper wire ground for trouble shooting...

Good Luck!

**pjmoreland** · 03-23-2021, 08:34 PM

The turn signals and the brake lights use the same bulb filaments, wires from the column to the rear of the truck and grounds. If the turn signals are working, but the brake lights are not, then I'm thinking you might have a blown fuse for the brake lights.

03-23-2021, 06:11 PM	#1
slowboy Registered User Join Date: Nov 2010 Location: WINSTON SALEM, NC Posts: 110	rear lights I removed my bed on my '72 GMC to have rockers and cab corners replaced. I had 2 aftermarket brake/turn lights strapped to the rear chassis so I could drive truck. I removed aftermarket lights, put my bed back on, connected harness to rear lights. Now the only lights working are the turn signal lights. The brake, park, and backup lights don't work. I've searched this forum but not sure what to do except make sure all lights are grounded to frame. I don't see a black ground wire from harness. There 'is' a brown wire from harness that's sticking out by itself. I tried grounding it to frame but that didn't help. Then I saw in Haynes book that that was the wire for License plate light. Please help... Thanks, Keith

03-23-2021, 06:31 PM	#2
Ironangel Senior Member Join Date: Feb 2010 Location: Falls City, Nebraska "100 Miles From Nowhere" Posts: 2,219	Re: rear lights The bed needs to be grounded to the frame...Battery ground to motor, motor to cab, cab to frame and bed to frame. I add extra ground straps on both sides of the bed and cab and I also run a ground from battery to frame as well...When a light starts acting up try using a jumper wire ground for trouble shooting... Good Luck! __________________ Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" "Be American, Buy American"

03-23-2021, 08:34 PM	#3
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,982	Re: rear lights The turn signals and the brake lights use the same bulb filaments, wires from the column to the rear of the truck and grounds. If the turn signals are working, but the brake lights are not, then I'm thinking you might have a blown fuse for the brake lights.

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