Hello all,

Having an issue with my battery dying because my tail lights and markers intermittently stay on after I park my truck. I get out, turn key off, everything is off. When I come out from the store or look in the driveway at night, my marker lights and tails are randomly on.

Anyone have ideas for me to try to resolve the problem?

1986 standard can pickup 22r

 

Upon looking at the schematic from the 87 FSM, the taillight relay controls both front clearance bulbs, both taillight bulbs and both license plate bulbs. Which means your relay may be getting a ground signal from the switch when it shouldn't (wire from switch to relay is red w/black stripe) . So either the R-B wire is grounding somewhere, the relay is jittery, or the switch is faulty. My guess would be the switch.

Also, the TAIL fuse gets energized from the relay via a red wire and then from the fuse a green wire runs to the 6 bulbs pig-tailing into a green w/light blue stripe wire. Another possibility is one of the R, G or G-L wires is getting energized by something other than the relay. Any trailer wiring, alarm system, or other non-factory wiring in this truck? Those trailer wiring pigtail taps are prone to corrosion over the years.

Again, I would check the switch first. And I have no idea if your 86 wiring for the lighting is the same as an 87?

 

From the 87 FSM

 

Thanks for the great information!

Nope, this truck is all stock electrically.

 

https://www.yotatech.com/forums/f131...85/index3.html

Post 52 in above thread shows great picture of fuse and relay location

 

Your dimmer switch combo contacts are probably shorting.
https://www.yotatech.com/forums/f131...l#post52314406

 

Thanks for all of the replies. I think I have it resolved after replacing the relay as mentioned above. I was going to wait a few more days just to be sure but if it comes back, I'll definitely reply back here.

Thanks again for all the help.