The other night my rear running lights stopped working. If I’m not mistaken, It seemed before that there was sometimes a slight delay in them coming on that I only noticed a few times. My dash lights work fine (I understand that they’re on the same fuse). Brake, reverse, signal and hazards are all functioning. So can I rule out a grounding issue?

so far I’ve tested
Voltage from the bulb sockets - zero, however the tail lights work still and are drawing 11.2v

Voltage from the fuse socket - 12v I’ve also tried a known working fuse and still nothing.

Continuity in the relay, which was a higher reading than to be expected but I can’t seem to replicate that reading. I have since then tried another working relay from a friends truck and still no luck. My relay also worked fine in his truck.

checked for chafing or broken wires along the frame rail and couldn’t see anything, I chased the wiring harness into the passenger side floor of the cab and still couldn’t see any chafed wires.

Anyone else have a similar experience? What else can I test or look for that might be a culprit?

thanks

 

Corrosion of the grounds serving the sockets of the tail lights. Known problem back there. They get corroded pretty easily. Check the ohms to ground. NO VOLTAGE. That will cause the failure of the ohm portion of a multimeter quickly.

Pat☺

 

even if the brake lights are still working a potential bad ground will cause the running lights to not? Is the ground essentially the portion of the socket where the light twists and locks into?

thanks!

tyson

 

Yes and yes

Pat☺

 

You said "No tail lights". How about front markers?
Measure voltage between wire to middle pin of connector and the outer metal cylinder. Should be 12V.
If you don't see 12V, keep red probe (positive) on middle contact. Move black probe to absolutely known good ground (i.e., ground of brake light). Should get 12V.. Then you know there's a break between ground and the outer metal cylinder of socket.