I am hoping that perhaps someone on the board has some knowledge on this subject. I own an '85 T/A with the LG4 and automatic. This was the first year for foglights. When I bought my car, the fogs didn't work. I know enough about the circuit that the headlights have to be on and in low beam. I have the GM service manual and it states that the relay is located on the drivers side fender near the firewall. There is a relay in that location but the wiring doesn't match the schematic. In fact, that relay seems to control the MCS on the carb. There are relays near the front of the car for headlight door actuators, but I don't find any relay that matches the schematic for the foglights. The wiring should be: BRN/WHT, LT GRN, PPL(2), and a RED/WHT. The wiring that goes to that fender mounted relay is: PPL, BRN/WHT, LT GRN, LT BLU(2). When I say (2), that means there are two wires of that color going into the relay. I have checked the foglight bulbs and they are good. I don't want to have to tear apart the dash looking for this thing.

gearhead141

 

 

This has to be the first good reply I've received. I thought that it might be somewhere other than the engine bay. I haven't checked it out yet, but I need to replace my remote dimmer, which is down there also. Thank you so much for the help. I don't think the fogs have worked in many a year.

 

I had the driver's side trim panel out over the weekend looking for the relay and could not find it. So Nina, could you supply a photo or be more specific. I looked a foot in front of the ALDL and saw nothing but firewall. I was on my back and looking upside down so perhaps my perspective was off a tad. At the same time, I was looking for the remote dimmer and finally found that. In order to replace that, I think I'm going to remove the lower dash trim. I couldn't actually see it, just felt it. If this fog relay is so hard to get to, that's probably why they haven't worked in years.

 

The relay is on the driver's side fenderwell immediately in front of the brake booster. Should have a four or five wire connector to it, held in place with one screw on an 'l' bracket.

The headlamps do not have to be on, but the parking lamps do. The relay's sole functions are to pass power to the fog switch only when 1) the parking lamps are on and 2) the high beams are off. Full power passes through the switch, it is not a switched relay. You can jump out the relay, bypassing it, if you desire independent action of the fog lamp switch.

There is no relay for the MCS.

If you ever need lamp/reflector replacement for your fogs, the Blazer brand, available at most parts stores and Walmart for ~$20 provides direct replacement pieces. Just put a second set into mine after a rock broke one of the lenses I had replaced several years ago.

 

Well Naf, that's the relay I thought was for the fogs but it turns out it isn't. And when I pulled the connector off, the clicking that was going on with the MCS stopped. So, that's why I'm stumped. As I stated in my original post, the wiring colors don't even match the schematic. I'm hoping NINA will come up with an explanation.

 

That was the correct relay. I just did some troubleshooting on my 85 TA LG4 yesterday afternoon when I replaced my fog lamps and they wouldn't light (turns out I had disconnected the connector to each when I removed the front cover some time ago). Five wire connector, if I recall correctly.

If unplugging it causes the MCS to stop clicking then something else is wrong. You may have a short or open (or both) that is letting power pass through this circuit to the engine controls circuit. Keep in mind that the MCS will only click for about 30 seconds or so if the engine is not started but the key is in 'run'. I'd duplicate that test, as it could have been a coincidence. There is no relay in line with the MCS. It receives voltage through the engine controls fuse and is grounded by the ECM (10 times a second).

With the parking lamps on and high beams off, the relay should click when it is plugged in AND pass power to the fog light switch. I had to replace my relay when I first acquired my TA in 2005, it had failed and was not passing power. I've had the wiring harness completely out during a tear down several years ago.

My three babies:



That was old, this is newer:

 

So Naf, can you tell me what the wire colors are on your '85 fog relay connector? I'm baffled as to why mine don't jive with what the service manual shows.

By the way, how do you like the Vortec in place of the old 305?

 

 

red and white (hot), green, brown and white and two purple wires. I'm in the garage with the TA right in front of me. I just chased these down the other day and confirmed continuity to the fog light switch.

Another pic of your car would help me stay motivated through my projects...

 

Wire colors could be different for different builds. I've found several discrepancies between wire diagrams and actuality (and between different wiring diagrams).

Vortec is in the 87 SC. Went a little conservative on the cam but it has great low end torque. The TA has a mild 350 with an LO5 cam. Perfect for everyday driving. Smooth idle and pulls hard to a blazing 4000 rpms...

 

So this is what the relay looks like in my car.

 

Here's a little wider shot showing the harness. So, there is no red/wht wire that I can see. Only one purple and two light blue. What do you make of that? The car was built the third week of Feb., 1985. NINA, now you can see what I'm dealing with.

 

Sounds like someone's bypassed the relay. Check your switch to see if it's got constant hot.

 

 

It's almost certainly been bypassed. Peel back that black tape (which isn't factory) and you may find the constant hot and the conductor to the switch shorted together.

 

OK, so I peeled back the electrical tape and this is what I found. The green wire had been butt spliced and came apart. There is damage to the insulation on the green wire, the brn/wht wire, and the purple wire. There is a brown wire with a harness connector that is open on one end. Something is not right here. Maybe you can post a pic of what it should look like Naf.

 

If you want it back factory, you'll have to identify each set of wires. You'll have:

) hot only with high beams on
) hot only with park lamps on
) constant hot
) power wire to fog light switch (you can test continuity on this one to the switch)
) ground

I can check mine (might be Sunday) and tell you where in the relay connector each goes.

You'll have to inspect your connector and determine whether it can be re-used or needs to be replaced.

In the meantime, after identifying them, insulate your hots from the park lamps and high beams and you can temporarily short the constant hot to the fog light switch to get them working. This will let them be switched on at any time with no 'buzzer' warning that they were inadvertently left on.

 

After further investigation, it appears that my foglight circuit has been rewired. The red/wht and one of the PPL wires have been replaced by the blue wires you see in the photos. Checking my schematic from the service manual, there is voltage across terminals "B" and "D" on the relay connector. This would be the red/wht and the PPL wires. My wiring is correct color wise from the switch to the relay. I can only guess that there must have been a short that fried the fusible link as well as some of the wiring. Finding the LTGRN wire pulled from the splice joint is probably what kept my fogs from working. I have some repairs to make and will give it a try when that is finished.

 

I made the repairs and put in a new relay and it still isn't working. I might have to pull the entire harness apart going from the relay down to the lamps. to see what's wrong.

 

do the checks I outlined and you'll find which wire is the culprit. need anything else from me?

 

Yeah, I need a quick fix. Oh, and I wish you were closer so we could hash this out together. Other than that, I'm good!

 

So it has been over a year since I started working on this problem. Life gets in the way and I just recently started working on it again. That's right, the fogs still weren't working all this time. Thanks Naf for all the help and encouragement. The one photo of my hand holding onto a brown wire turned out to be the culprit. This is the wire that actually closes the switch to provide power to the relay. I found the other end of the brown wire coming through the firewall with a brn/wht and a ppl wire. A short length of wire spliced in and I now have fog lights once again. I can only guess that there may have been an overload in that harness and it was rewired. The incorrect colors threw me off.

I just wanted to close out this post and thank everyone who chimed in to lend a hand.