Hardwired brake light issues - can't find the problem

[NjDL]

I got a 1989 244 DL and have been bringing it back to working order. I got everything running, but the last problem that needs to be ironed out is the brake lights. No matter what I try, the lights won't come on.

So far I have:
-made sure all bulbs work
-Checked voltage at taillight wires with brake pedal down, checked diagrams
-Checked fusebox and red/green to brake switch, voltage there
-Bypassed brake pedal switch by connecting wires
-Connected another wire straight from red/gn wire to brake light

Still nothing. It doesn't make sense to me that if I am getting voltage from the red/green wire, and if it is connected directly to the bulb, that it wouldn't light up. Am I doing something obviously wrong?

Thanks!

 

[mikich]

You might need a new bulb integrity sensor.

 

[ortho stice]

Is the ground path okay? So bulb socket is grounded?

 

[the_hairy_baboon]

Is the ground path okay? So bulb socket is grounded?

add in the difference between a local ground (to what's theoretically body and common with negative battery terminal) and actually going to negative battery terminal. For example, a rusted ground bolt might have 5-10 ohms resistance, which means ground is not true ground and it's like adding another bulb in series that reduces current flow (and hence filament doesn't glow)

 

[ZVOLV]

Get a test lamp, not a meter, and shake down the circuit. A test lamp will also confirm the integrity of your ground circuits.

Start at the pedal switch, then to bulb out relay (round red thing), and then back from there.

As mentioned the red bulb failure relay could be bad. It may be worth a shotgun

 

[NjDL]

Ok. I think I figured it out. The bulb failure relay is shot, and isn't connecting the brake lights up anymore. Fuse 7 was corroded enough to only connect intermittently and make it seem like the problem was something else, but I replaced it and traced to the relay. I'm gonna open it up and see if anything's glaringly wrong, but I'll order a new one if not.

Edit: Couldn't find anything super obvious, for now I'm just gonna connect the wires inside the relay to bypass it

Thanks a lot for the help!