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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: ih8vols on April 15, 2023, 07:24:45 pm
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79 Silverado stepside
About a year ago I upgraded that lights to LED’s so they would be brighter. Everything worked fine.
If the truck sits for too long, there’s times the rear lights won’t work at all (blinkers, sidelights on rear, brake lights). The couple times I’ve fixed it by retightening the grounds from the tail lights to the bed. It fixes it.
Last weekend, I went to drive the truck and realized the taillights weren’t working. Backed it into the garage. Did my usual tightening of ground wires and they worked. I pulled the truck into the driveway and they stopped. The license plate lights still worked.
Tried my ground wire trick again. Nothing. Jiggled the rear harness and the license plate lights went out.
The previous owner had added trailer wires before the rear harness plug and it was a ball of crazy. I decided to cut that mess out and cleanly wired everything back up. Still zero lights.
I disconnected the grounds going to the side markers and put them to the bed with the tail lights. Nothing.
I added a ground strap from the side marker ground and tail light ground to the frame. Nothing.
All the fuses are fine.
I checked continuity with my multimeter on the intermediate harness and got a current.
Any more ideas on what I can check? I’ve spent hours on this thing today and gotten nowhere.
Appreciate it.
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I know LED's introduce some variables but it sounds like it's still a ground connection issue.
Look for a product called DeoxIT D5. Spray it on all connections you can associate with your rear harness.
Pls let us know what happens.
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Do you have an incandescent test light?
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Do you have 12v at the relevant bulbholders when they are operated?
Check resistance to a good ground from each bulbholder ground connection, should be low maybe 1 or 2 ohms.
Let us know what you find.
Graham