It's an 85SE V6. To begin, the right side would raise but not lower. It has been rebuilt with Rodney's metal gear. Left side would operate normally, up and down.

Motor relays were swapped side to side to test. The problem didn't go with the relay, so the motor relays are good.

The isolation relay circuit has been tested with 3 known good relays, so I know that one side of the isolation relay isn't dead.

The limiter switch has been replaced with another limiter switch.

The light switch has been tested with a known good switch, then the original was reinstalled. Same result with both switches.

Next, the internals of the motor were replaceld. Still no change.

Last step, the motor case was replaced with the same result.

In short, the Isolation Relay, the Motor Relays, the Limiter Switch, the internals of the motor and even the external case has been replaced and I still have the problem that the right headlight will go up, but not down.

Within the last half hour, now both headlights have stopped going down. They will go up, but not down.

All relays click when the light switch is activated to ON or OFF, so It appears that power is going to each motor relay and thus to the limiter switch, brushes.

Any suggestions? Not going to change it to a Generation 2 system, so don't go there. It's someone else's car and she can't afford it. My work on the car is gratis.

Test for 12v at the blue wire single connector, on the wiring harness side. Should have 12v with the headlight switch off.

Thanks. Will do tomorrow. Where is that wire powered from? The left one works fine.

They both feed back into the isolation relay. One side is blue, other side is blue with a white tracer. If you get a test light to light in the above steps, the problem is within the motor. No test light, it's in the wire or isolation relay.

The blue wires will obviously be outbound to the motors from the relay. The wire diagram shows a white wire feeding into the isolation relay from the firewall side of the harness to control both blue wires

Three different motors and at least as many isolation relays. I even swapped out several limiter switches.

I left the isolation relay off it's mount and hanging upside down last night. We had torrential rains and this morning neither headlight would work. Replaced the relay and still nada. Found a blown 20 amp fuse that also fed the blue dingy thingy and the left headlight began working. Right one still didn't go down. It goes up, but not down. I checked power on both motor relays and get the same on both, but I didn't know the blue wire was a hot wire. I thought it was just a ground. I guess that explains why the lights will go up with it unplugged, but not down.

The sole purpose of the blue wire is to make them go down. Known functional relays to try are about the only way to verify a relay problem with ease. I have an 86 GT and an 85 trans am with identical headlight setups. I hesitate to even try removing a good relay for testing purposes. But if you open a relay up (remove that square black housing), it sometimes reveals a blatant failure.

Typically, an isolation relay failure will display a failure to both headlights, but I wouldn't count on that 100%. Better to check grounds, wires for damage, and even pulling the side cover to expose the limit switch (while manually turning the knob to observe function) is a safer bet. Pulling the headlight assembly completely, and manually testing the motor with said cover removed while the motor is still installed would be preferable. This allows the motor to reach the stop points so the contacts show movement within the limit switch. Lastly, a 6V battery is a convenient jumper if you wish to apply voltage to the blue wire on the headlight motor assembly, with an appropriate ground.

I have not jumped any gen 1 motors for testing, but have done as much on gen 2 motors with ease.

I have about a dozen isolation relays and about the same number of good limiter switches. I've tried several of each. With the lights raised, I've manually turned the motor further in the up position to test the opening of the limiter switch. Still won't go down when turned off. Something strange I found is that the motor relay has one terminal that isn't used. That terminal has 12V on it.

I just checked and I have 12+ volts on each of the blue wires. The schematic shows they're powered from the isolation relay, so that indicates the relay is good.

[This message has been edited by fierofool (edited 07-18-2018).]

Where is Ground Terminal S103?

S103 is a splice.

Grounds start with 'G'.

Since I have power through the relay and ground for the UP, and I have power for the DOWN, is it safe to assume that I have no ground for the DOWN? This would indicate that there are two separate grounds to the motor? If so, I could see where a splice might be a problem. Though I swapped the left relay to the right, just to be sure my used motor relays weren't all bad, I purchased a new relay and got the same results.

I believe the two grounds share the same screw as two ring terminals to the driver side fender near the hole where the side marker wiring feeds through to the fender.

Thanks. I had to return the car to her, but next time I'm in the area, I'll check that ground. I did have to replace the terminal on the right fender wall. Seems the shield on the headlight was catching it and had broken the wire but the insulation was still holding it in place. That still didn't solve the problem.