Total Brake Light Failure - Diagnostic Complete
#1
06-06-2021, 07:24 AM
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Total Brake Light Failure - Diagnostic Complete
Hello everyone and thanks for helping out.
I have a 93 245 in good working order. I discovered yesterday that all of my brake lights are non-functional.
I found the old threads and this is what I can confirm.
Brake Switch is good - No current when open, current when closed.
Bulb Failure Relay - Checked solder joints, look good. Checked function, all seems to be correct. I'm getting 12.5v on the correct pins.
No power at the taillights. (obviously, but confirmed with the meter)
Bulbs are good.
What else can it be after the bulb failure relay? I didn't find any threads that go into what to look for after that. There was some mention in the threads of a circuit board on the lamp housing, but I think that may only apply to the sedan as I couldn't see any on the wagon housing.
My current understanding is that there really isn't anything but wire after the relay. I did inspect as much of the wire under the carpet as I could, but didn't see anything obvious.
Other things to note that I don't think impact this but maybe it does:
Within the last few weeks, my driver side window switches started acting up. They won't work, but if I open the door and close it again, they do.
I installed my trailer hitch.
Thanks,
Joe
I have a 93 245 in good working order. I discovered yesterday that all of my brake lights are non-functional.
I found the old threads and this is what I can confirm.
Brake Switch is good - No current when open, current when closed.
Bulb Failure Relay - Checked solder joints, look good. Checked function, all seems to be correct. I'm getting 12.5v on the correct pins.
No power at the taillights. (obviously, but confirmed with the meter)
Bulbs are good.
What else can it be after the bulb failure relay? I didn't find any threads that go into what to look for after that. There was some mention in the threads of a circuit board on the lamp housing, but I think that may only apply to the sedan as I couldn't see any on the wagon housing.
My current understanding is that there really isn't anything but wire after the relay. I did inspect as much of the wire under the carpet as I could, but didn't see anything obvious.
Other things to note that I don't think impact this but maybe it does:
Within the last few weeks, my driver side window switches started acting up. They won't work, but if I open the door and close it again, they do.
I installed my trailer hitch.
Thanks,
Joe
#2
06-06-2021, 09:14 AM
May be it has to do with installing the trailer hitch. Did you also wire the trailer plug and associated? And how sure are you that the failure relay is not the culprit? How did you check its functions? It can fail in many different ways, it has several circuits. I'd be inclined to think the relay is at fault.
#3
06-06-2021, 10:18 AM
Did you use a wiring adapter to convert the brake and turn signals to one bulb? (5 wires in a Volvo, 4 wires in trailer adapter park/ground/left brake-turn/right brake-turn)
If your brake lights failed when you installed the trailer adapter (actually you did not say you installed one - just the hitch) disconnect the trailer harness.
The brake lights have 3 separate wires from the failure relay to the bulbs - I would expect the center brake light wire to be broken in the tailgate hinge - but the other 2?
If your brake lights failed when you installed the trailer adapter (actually you did not say you installed one - just the hitch) disconnect the trailer harness.
The brake lights have 3 separate wires from the failure relay to the bulbs - I would expect the center brake light wire to be broken in the tailgate hinge - but the other 2?
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