QuestionQUESTION: I will do my best to keep this brief but provide needed info...1991 740 Turbo Sedan...here are the facts as I know them...
1. Recently slid into guardrail causing drivers side damage including tail light and turn signal. Both replaced.
2. Drivers Side Tail Light - 2 black wires are loose appear to have come from same, now empty, space in the plug, but I cannot find a diagram for this part. Running light and turn signal and emergency flashers all work.
3. Speedometer has been intermittent for past several weeks prior to collision. I mention this as I have seen some postings that this might have to do with the bulb failure relay?
4. After replacement of tail light fixture I have no brake lights (none in any of the 3 locations) and bulb failure lamp is on whenever light switch is in the on position(does not matter if brake pedal is pressed or not). I have tried to hard wire the loose black wires @ the tail lamp but no affect - still no brake light and still have failure lamp. Bulbs all appear to be good. Brake light Fuse is intact.
My questions...need to confirm wiring for DSide tail lamp so I can permanently fix this and to be sure this is not causing the other problems.
Is there any way to diagnose the bulb failure relay short of replacing this $80+ part? Is this a likely cause?
I have not yet accessed the brake light switch. Can you confirm the location and the best way to diagnose if this is the problem? (I read there may be 2 switches, is this correct?)
Thanks!
ANSWER: I don't have access to wiring diagrams at this time. But it sounds like you may have an earlier style assembly. Check the part number against what the dealer says it should be.One black wire, from the small corner bulb should go to ground and there is a black wire coming off the printed circuit that should go to ground. Taillamp assemblies may look the same but have different printed circuits. Try swapping the printed circuit from the old assembly.Figure this part out and worry about the sensor if it is still an issue. Brake switch is located down at the pedal. The long black plastic one with a vacuum hose going to it is for the cruise control. The one for the lights is above it and pretty well protected from trying to get a test light in there, drop the knee bolster for easier access.17mm wrench to loosen the nut, not alot of room.Again though I believe your problem lies in the taillamp assembly
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QUESTION: Thanks for the quick response. I did swap out the board (mine seems to be in bette condition anyway). Back to the wires. To be clear, or at least try to be clear - I have 2 loose black wires to deal with. These are along with all of the other wires (approx 8 wires total) that go into a plug that in turn plugs into the tail lamp board. There is one empty spot in this plug. How can I determine which of these 2 wires goes into the plug, and what do I do with the other wire?
ANSWER: Trace the wires back to where they come from. Correct me if I'm wrong. One is coming from the printed circuit,right? The other one is coming from the little push in bulb on the corner, right? Both should go to ground. Just unscrew one of the mounting bolts for the taillamp assembly and make sure the connectors, should be round eyelid connectors,are making a good connection to the metal.If its different let me know
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QUESTION: I have more detail. The 2 black wires do not come from the same source One cones in from the front of the vehical and the other goes to the right tail light. Do these both do to the same terminal on the left tail lamp?
ANSWER: What kind of connectors are on the ends?
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QUESTION: They are loose, assume they came loose in the collision - that is the problem...I have one empty slot in the plug to the CB but not sure what to do with 2 wires. Used alligator clips to try and connect but no success - Until I am sure I have these wire installed correctly trying to diagnose any other issues is impossible.
ANSWER: That is for sure. I will try to get wiring diagrams tomorrow
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QUESTION: Thanks - but I have an update. The 2 black wires are for the back up lights (they do go together for future reference) and they now work. Still no brake lights (all 3 do not work) I checked the brake switch on the pedal. I have continuity across when the pedal is pressed and it passes 12 volts thru when the pedal is pressed. What next?
ANSWER: Are you getting twelve volts all the way back to the brake lights?
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QUESTION: No, I am not getting 12V at the brake lights, and I have yet to figure out where/how to access the 3rd light (I have already snapped and broken a few plastic parts on this project - I am gettting a little leary of pushing or pulling too hard)
AnswerCheck the bulb failure sensor.Located in the central electrical unit behind the ashtray.Round and either red or yellow in color.The cover can be pried off allowing you to inspect the solder connections.Once you get the cover off turn it so the connection pins point up and look for solder connections with cracks around the pins.You can resolder the connection and/or replace the sensor.
