Bulb check unit causes tail light failure?

[dtw]

My mechanic and I have been starting to go through some electrical issues. All my exterior lights have been working perfectly, but my bulb check unit has been throwing idiot lights for tail lights and brake lights (both of which work(ed) perfectly). He opened up the unit and found a failed solder joint, which he fixed. That caused the tail light warning to go out. However, when I picked up the car, I had no tail lights (again, everything was working fine before messing with the bulb check unit).

My question is this - can a bad bulb check unit cause the tail lights to actually stop working? Or is this a coincidence, and there's something else at work. Yes, the fuse tested good and the bulbs are brand new.

As a side note - does anyone have a tested good bulb check unit for an '85-'86 S3?

[neil30076]

Originally Posted by dtw

My mechanic and I have been starting to go through some electrical issues. All my exterior lights have been working perfectly, but my bulb check unit has been throwing idiot lights for tail lights and brake lights (both of which work(ed) perfectly). He opened up the unit and found a failed solder joint, which he fixed. That caused the tail light warning to go out. However, when I picked up the car, I had no tail lights (again, everything was working fine before messing with the bulb check unit).

My question is this - can a bad bulb check unit cause the tail lights to actually stop working? Or is this a coincidence, and there's something else at work. Yes, the fuse tested good and the bulbs are brand new.

As a side note - does anyone have a tested good bulb check unit for an '85-'86 S3?

Bad bulb check cannot cause brake lights not to work, more likely bad ground under rear passenger side qtr panel, or bad brake switch ( which is common). Does the light go out if you press the ! button?
Where in raleigh are you, i'm south in apex.
Neil

[dtw]

Originally Posted by neil30076

Bad bulb check cannot cause brake lights not to work, more likely bad ground under rear passenger side qtr panel, or bad brake switch ( which is common). Does the light go out if you press the ! button?
Where in raleigh are you, i'm south in apex.
Neil

Not brake lights, tail lights. Brake lights are working fine.

Idiot light in pod does not extinguish when I push the ! button, no. But the ! does stop glowing red when I push it (as I do every single time I fire the car up ).

[Mrmerlin]

check the fuses

[dtw]

Originally Posted by Mrmerlin

check the fuses

They're fine as stated in the OP.

[neil30076]

Originally Posted by dtw

Not brake lights, tail lights. Brake lights are working fine.

Idiot light in pod does not extinguish when I push the ! button, no. But the ! does stop glowing red when I push it (as I do every single time I fire the car up ).

Sorry, my bad, The tail lights, front running lights and side markers are called the clearance lights in the wiring diagrams. I assume that is what you are referring to and they are all out? You say fuses 40 and 41 are ok. If only the back is out check for 12v at the lamp test module on pin 5 and out from the lamp check unit connector pin 3 to the rear lights. And yes, a bad check module can cause the back clearance lights to fail.

[dtw]

Originally Posted by neil30076

Sorry, my bad, The tail lights, front running lights and side markers are called the clearance lights in the wiring diagrams. I assume that is what you are referring to and they are all out? You say fuses 40 and 41 are ok. If only the back is out check for 12v at the lamp test module on pin 5 and out from the lamp check unit connector pin 3 to the rear lights. And yes, a bad check module can cause the back clearance lights to fail.

Neil, thanks. Yes - 40/41 are good, only the back tail lights/side markers are out. We'll try what you mentioned.