I am still in pursuit of why the Taillight warning light comes on in our 84S. All the back bulbs are working and all are identical on each side of the car.

What is suspicious is the wiring to the passenger's side back sidelight. The wiring was supplemented with a 3" wire segment that was connected to the lead wire via a wire crimp. The picture shows that I've separated the two pieces.

The lead wire copper is very blackened - almost like tarnished. The corresponding ground wire is okay. Might the blackening cause an impedance differential with the driver's side of the car? (And thus the warning light?)

I can't seem to figure out where this wiring goes as it proceeds back into the car. If I was to try to rewire this area completely, would the (damn) bumper have to come off? That might become a PITA. Otherwise, I'll just put female connectors on the end of the lead and ground wires and call it a day.

Thanks as always,
Tim

 

more than likly the wire got damaged and that it was fixed and then it got wet, getting wet is common for the rear side lamp connections as they run along the floor at the rear of the hatch, and somtimes the hatch seal leaks, you might try tinning the wires first use some flux to clean the wires then tin them then crimp them, or best choice is solder them and heat shrink

 

The rear marker lights and the rear/side markers are monitored together...(same circuit) while the front/side markers are not monitored.

any oxidation is most likely to affect a connection (not the wire itself - a well cleaned & soldered connection sould fix that) a crimp or IDC connection to this condition wire may be very poor initially or may degrade quickly even if it appears OK initially.

If you need to test - simply connect a bulb of the correct type (same as a rear/side marker) in place of this wiring to the side marker feeder and see if that fixes your problem if yes - you need to clean that up.

Alan

 

Will get some flux for this - thanks Merlin!

Um, what do you mean by the side marker feeder? Location? If I have to rewire, will I have to remove the bumper? Merlin refers to the floor of the hatch...?

Thanks mate!

 

No, you shouldn't need to remove the bumper for this.

This might help:
S1 powers left side marker and left tail, and is hot when the headlight switch is on.
S2 powers right side marker and right tail, ditto.
S6 powers the stoplights

F7 is signal from the stoplight switch

The bulb control unit is near the passenger shelf, wires are routed through there. The wires pass down the right sill of the car towards the hatch area. You might want to be sure somebody hasn't partially bypassed the bulb control unit. Its all complex, you might have to patiently trace stuff.

I know this from having sorted out some issues recently on the same year car and studying the diagrams, but am by no means an expert. The diagrams are an absolute must-have. The 83 and 84 are very similar, and the 83 diagrams are much more clearly written, so as you work the project over tiime you may find both sets useful.

 

you will also need a soldering iron to make the flux work, the connectors i am referring to are near the rear tiedowns in the rear corners of the hatch . They get wet and the wire connectors corrode, it looks like your connectors may have been damaged and somone put a fix in place but the wire has gotten wet again and is now corroding

 

Couple more things.

The bulb control unit compares the stoplights, it compares the rt tail + marker to the lt tail + marker.

There are sensors in the master cylinder for fluid level, not sure what warning light is kicked off by these relative to brakes. Don't think its the one you are chasing, but thought its worth mentioning.

If you search on this BCU or bulb control unit, you will find some information, including how to jumper past it. Unfortunately, its all not perfect information, so use it carefully of course. Maybe your wiring fix will equalize the resistances, but you would think it would not kick-off the warning. We will soon find out, eh?

My BCU was fried inside. Caused tail and marker on one side to be inoperable. Could likely have manifest itself in other ways, too, but this was what I found.

If you want access to the backs of the taillight assemblies, then the bumper cover needs to come off.
(That's what I did yesterday in order to fix my corroded license plate light fixtures and to remount my loose and broken taillight mounts). We can gin-up pictures if you really need them. My interior is out and bumper cover is off, so all the stuff is exposed.