Tail light wiring harness - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**rs74** · 01-24-2013, 12:09 PM

All the rear lights on my 85 shortbed don't work any more and I suspect a mouse. I haven't got under the truck or pulled the bed yet but can a new harness be bought that goes from the firewall all the way back.

I might have issues with the fuel gauge not reading either. That might be a separate issue. My truck has sat since 06 and I only get it out and start it about twice a year. But that is all about to change if everything goes right. Time to get the ol girl back on the road.

dieseldawg142 · 01-24-2013, 12:39 PM

if you have no lights at all, check your connectors & plugs first.most squares have a taillight harness plug behind the cab, i just picked up some replacement wire & a new plug & re-did the harness, 4 wires, very simple, also put some convoluted tubing on them, they really take a beating back there.check where your wires go past the exhaust under drivers floorboard. what is your fuel gauge doing(what happens to needle when you turn on?). i just went threw this, needle would sit at 3:00, turned out sender wire was rubbing on a clamp

**rs74** · 01-24-2013, 12:54 PM

I will have to get under the truck and try to trace down the wires. It has been awhile since I noticed it and forget if I looked at the wires. They used to work just fine and one day they didn't. May just be a bad connection.

I don't think the fuel wires run along with the tail light wiring. I may be wrong about that though. IIRC the fuel gauge acted like it was past full but then after moving it it came back to show how much fuel there was. Bad ground? or does that mean it is going to ground.

dieseldawg142 · 01-24-2013, 02:06 PM

does the gauge read normal after it spiked? after sitting for an extended time the sender might have been stuck, corrosion on your grounds build up, connectors rust. i would put fresh fuel & some cleaner in the tank, check & clean your grounds, & check wiring for breaks.the sender wire joins the taillight harness right after the t.lite harness connector behind cab, & they run past the exhaust, another good spot to check

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my 85 crew has a plug at the lights & one at rear of cab, also where sender wire ties in, not the best pic, farthest left red conduit is t.lites

01-24-2013, 12:09 PM	#1
rs74 Senior Member Join Date: Jun 2010 Location: Illinois Posts: 2,957	Tail light wiring harness All the rear lights on my 85 shortbed don't work any more and I suspect a mouse. I haven't got under the truck or pulled the bed yet but can a new harness be bought that goes from the firewall all the way back. I might have issues with the fuel gauge not reading either. That might be a separate issue. My truck has sat since 06 and I only get it out and start it about twice a year. But that is all about to change if everything goes right. Time to get the ol girl back on the road.

01-24-2013, 12:39 PM	#2
dieseldawg142 Registered User Join Date: Jul 2011 Location: back 40, bc Posts: 3,903	Re: Tail light wiring harness if you have no lights at all, check your connectors & plugs first.most squares have a taillight harness plug behind the cab, i just picked up some replacement wire & a new plug & re-did the harness, 4 wires, very simple, also put some convoluted tubing on them, they really take a beating back there.check where your wires go past the exhaust under drivers floorboard. what is your fuel gauge doing(what happens to needle when you turn on?). i just went threw this, needle would sit at 3:00, turned out sender wire was rubbing on a clamp

01-24-2013, 12:54 PM	#3
rs74 Senior Member Join Date: Jun 2010 Location: Illinois Posts: 2,957	Re: Tail light wiring harness I will have to get under the truck and try to trace down the wires. It has been awhile since I noticed it and forget if I looked at the wires. They used to work just fine and one day they didn't. May just be a bad connection. I don't think the fuel wires run along with the tail light wiring. I may be wrong about that though. IIRC the fuel gauge acted like it was past full but then after moving it it came back to show how much fuel there was. Bad ground? or does that mean it is going to ground.

01-24-2013, 02:06 PM	#4
dieseldawg142 Registered User Join Date: Jul 2011 Location: back 40, bc Posts: 3,903	Re: Tail light wiring harness does the gauge read normal after it spiked? after sitting for an extended time the sender might have been stuck, corrosion on your grounds build up, connectors rust. i would put fresh fuel & some cleaner in the tank, check & clean your grounds, & check wiring for breaks.the sender wire joins the taillight harness right after the t.lite harness connector behind cab, & they run past the exhaust, another good spot to check my 85 crew has a plug at the lights & one at rear of cab, also where sender wire ties in, not the best pic, farthest left red conduit is t.lites



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