SC Tail Light Wiring/Mechanics

[BrokeMyCar]

I'm trying to trouble-shoot what the search reveals to be a typical problem: brake lights and reverse lights not working! They don't work, but they do blow out fuse 4 only intermittently. The heater fan fuse appeared to blow at the same time.

I've ruled out (and removed) a few components (like the engine-compartment light, and the heater fan, and the bulbs are all good), but the problem persists. Now I'm digging through tail light assembly and could use some help. Specifically:

1) Does anyone have the pin-outs of the round plug that goes to the left rear wiring harness?

2) The bolt on the in-side of the assembly is brokwn into two parts so I can't remove the assembly. Any suggestions on its removal? It's a sketchy proposition to Dremmel somewhere I can't see!

Thanks,

Babak

[Bob Kontak]

Left rear blinker bk/wt Fuse 10 (5a)
Left rear marker and tail light gr/re Fuse 4 (5a)
Brake lights both sides bk/ye fuse 15 (8a)
Eng comp light Fuse 4
Backup lights (both sides) gr/br Fuse 11 (16a)
Rear blower is separate from the above circuits. Is fed from connection 87 on the heater ventilator relay. Pin 86 Fuse 22 (25a) Pin 30 Fuse 23 (25a)

[BrokeMyCar]

Thanks for the fuse connections Bob. I ohmed out the pins to ground and found an anomaly between left and right rear lights. Unfortunately I can't see how to correspond the pins to the wire colors as the connection is sealed. Does anyone know what the pin immediately clockwise to the notch (looking at the cable, not the housing) is for? It reads 87ohms on the right, infinite on the left.

[Bob Kontak]

The wire to the engine compartment light is not switched. If it touches a ground it will blow #4 fuse.

I will see if I can figure out the pin question in the morning.

[BrokeMyCar]

Thanks Bob- I temporarily removed the engine compartment light to rule it out. So far no blown fuses but the brake/backup lights still won't turn on.

I also pulled the #4 fuse and put a voltmeter across the contacts with the connections to the light housings unplugged. With light knob pulled it read 12v which tells me there's a short somewhere between the fusebox and the plug into the light housing. That pin is my best lead so far as to tr cause, would love any more information you have about it. Thank you very much!

Babak

[ossiblue]

Originally Posted by BrokeMyCar

Thanks Bob- I temporarily removed the engine compartment light to rule it out. So far no blown fuses but the brake/backup lights still won't turn on.

I also pulled the #4 fuse and put a voltmeter across the contacts with the connections to the light housings unplugged. With light knob pulled it read 12v which tells me there's a short somewhere between the fusebox and the plug into the light housing. That pin is my best lead so far as to tr cause, would love any more information you have about it. Thank you very much!

Babak

You may be dealing with three separate issues here--the blowing of fuse #4 and the non-functioning brake and back up lights. It sounds like you're on the trail of the fuse problem but the brake lights may be a bad switch(s) in the master cylinder and the reverse lights may be a worn pin in the transmission switch--both are common failures.

You can test the brake switch by disconnecting the lead at the MC and checking for voltage (ignition on.) If present, the fused circuit is good. Reconnect the leads, have someone depress the pedal and measure voltage at the connector of the brake light. If no voltage, bad switch.

Similar test for the back up light. Disconnect the wiring to the back up switch on the trans and "jump" the two pin connectors on the wires. Turn on the ignition and see if the reverse lights are on. If so, switch is likely suspect. If not, use a multimeter or test lamp and test each pin on the wire for voltage. If neither wire is hot, problem is between ignition and switch. If one wire is hot (as it should be), problem is between switch and lights.

If you want to test the switch, put the car in reverse and turn on the ignition. You should get voltage at one of the connector pins on the wires. If you have a needle probe on your multimeter (or test light), you can plug in the known hot wire to the trans switch and put the probe in the other hole. If no voltage, then the switch is bad and it's likely the pin.

[Bob Kontak]

Rear six prong plug on drivers side with notch at 12:00

12:00 Tail lights
2:00 Don't know yet
4:00 Don't know yet
6:00 Tail lights
8:00 Brakes
10:00 Blinker

My reverse switch at the trans has a bunged up wire - fixing now and will post when I have the correct pin.

That leaves one unknown pin. What else could it be. A ground for the light assy?

Also replicated your #4 fuse test - nope - 12 volts is what I get with lights on and fuse removed putting leads across the fuse contacts. My tail lights and marker lights are ok.

[Bob Kontak]

Here is the update

4:00 is the reverse light.
2:00 leads to nothing that I can tell - and I removed the tail light assy.

A white and green wire enters the male connector but there is nothing that I can see that connects to it past that pin. Wiring diagram shows a white and green wire feeding the tempostat motor for cruise control but I don;t know if that would be the feed pin if you had CC.

The license plate light ties into the tail lights somewhere in the cord downstream of the female connector.

I tested the circuits with a volt meter pushing on pedals and switches AND the removed the tail light and checked each line from the tail light to the female connection.

Glad I did it as my tail lights are dirty inside and I found the bad reverse light wiring.


+1 on ossiblues comments.

Also there is an "ok" wiring diagram for an 82 SC in the tech info center to help you figure this out.

[kiwiokie]

The spare connector on the driver's side is for the Euro fog light. The same connector on the passenger side is used for the oil level sender.

[Bob Kontak]

Yes - I did see the oil level unit wire heading in that direction under the car but did not have a clue about the spare pin on the drivers side. Thanks.

That pretty much confirms things regarding the mystery pin.

Brokemycar - One circuit at a time. 4 fuse is tail lights - not brakes. Focus on the reverse lights as they are on a simple circuit and you will feel like you are making progress once fixed.

[BrokeMyCar]

Thanks everyone, this is amazing information and I'm really thankful for the effort you guys have put into assembling/gathering it. It is totally consistent - the difference between the left and right sides I saw is on the pin that's the fog light on one side and the oil level sender on the other. So much for my clue.

Hopefully I'll arrive home early enough tomorrow to try fixing it again. I don't like jacking/working under the car at night, so I'll have to start with the brake switches and fix the reverse lights over the weekend. If I understand the drawings correctly shorting the leads to one of them should be enough to turn on the light, if all else works.

Thanks, I'll be sure to update when I get to the bottom of it -

Babak

[RWebb]

thx for the pin-out ID

[BrokeMyCar]

I only had a few moments out there with it tonight. I disconnected the plug to the brake switch at the master cylinder, and ran 12V (fused) to the gray/yellow wire that was supposed to lead to the brakes (key at ACC). It lit up only the passenger-side tail lights (not brakes).

Turning on the car's main lights turned off the previously lit passenger side tail light, but turned on the driver's side tail light and both rear side markers. In hindsight the turning off of the previously lit light may be due to switching from the power I drew on in the fuse box (can't remember which one I used).

Seems I must have a broken connection along the way. Any suggestions on places to check? With Bob's information I can now look for continuity between the 8:00 prong on the light-housing connector and the yellow/gold wire going into the brake switch, but there's a lot of cramped car space between the two.

Thanks all,

Babak

[magnuskgc]

can somebody post what color wire goes to what?I am having the same problem.. I have 5 wires.. and I see where they connect inside the tail light bucket.

black/white
grey/red
gery/grown
brown
black and yellow.

[RWebb]

somebody post a close-up pic of the connector, and we can then photoshop in the wire colors

BTW - IIRC, old cars (my '73.5) have the pins numbered on the schematic, so there might be some visible remnant numbers on your connector

[magnuskgc]

Not the best but maybe it can work... not that the one black wire should be black and yellow (up at top there is a butt connector.
and this is the passenger side tail light connector

[Bob Kontak]

[Bob Kontak]

Sorry - thought you had an SC

[RWebb]

a PO really effed with your car!

[Bob Kontak]

Magnuskgc - I hope this does not turn this into a complete hijacking of BrokeMyCar's thread.

Is your problem the brake lights and reverse lights not working or (and?) you don't know where the wires go?

I will look at the schematic for the year body you have and let you know what is what. Those wires look old - old like early 1970's vintage. I have the factory manuals for that but not the 86.

Please advise.