tail light housing grounding

[Lz7w]

the other day, I noticed that my left front parking light was coming on when the car is in reverse. while looking into the issue (checking and cleaning all the grounds for the tail lights, etc.), I was surprised to see that the tail light housing isn't grounded until it's installed with the 2 mounting screws! (the ground wire is installed properly--from a bumper-mounting bolt to the inside of the housing cover plate.)

is this actually correct or should the housing always be grounded with the ground wire connected? thanks!

[dho]

Lz7w, on my '71T, the rear taillights are grounded to the rear-most bumper bolt, as you mention. There is not a separate ground wire for the housing itself.

dho

[Lz7w]

thanks, let me clarify since I think my question might not have been clear:
terminology I'm using below:
- tail light housing: the part that holds the bulbs and has the wiring terminals on the back
- tail light cover plate: the plate that covers the back of the housing; attaches to the tail light housing with 2 screws (from behind the bumper)
- tail light assembly: housing + installed cover plate

scenario #1: tail light wires connected, cover plate attached with screws, but assembly not installed in the car
bumper bolt -> ground wire -> 'cover plate' terminal (on the inside of the cover plate)

in this case, if the assembly is fully connected but not installed to the body with the 2 mounting screws, the housing isn't actually grounded (i.e. lights don't work).

scenario #2: scenario #1 + adding a jumper wire with the assembly still not installed in the body
bumper bolt -> ground wire -> 'cover plate' terminal (on the inside of the cover plate) -> jumper wire -> tail light housing

in this case, the housing is grounded and the lights work as expected.

if I remove the jumper wire and install the assembly into the body with the 2 mounting screws, the housing is grounded and the lights work as expected.

so my question is whether the housing should actually be grounded in scenario #1. based on the wiring, I would think that it should be--seems like that's the whole point of the ground wire--but since the the housing has a gasket around the back opening, it also seems like it's insulated from the cover plate.

[edmayo]

Yes, the screws must be touching the tail light cover. Use an ohm meter and trace the conductivity of the ground path, bulb socket, light housing, ground wire from bumper bolt grounded at spade spot welded to cover plate, cover plate only picks up ground from housing thru the two screws. We've seen corroded screws prevent grounding and bulb function. An ohm meter test will prove all of this. This is a normal part of diagnosis.

[Lz7w]

thanks Ed!