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Hi All,
I continue struggling to get my headlight to work. My headlight power on but the motor do not flip them open. However if I have them open and turn them off, the headlights turn off and the motor closes the headlight. I have tried replacing the isolation relay but no luck. Only the bulb turns on. I tried directly giving power from the battery to the motor and had luck there. The motors opened the headlight beautifully. Has anyone had this issue and have any guidance on how to solve this. Thank you in advance.
The headlight switch supplies voltage to 1 wire when pulled on and to another wire when turned off. The supply to the switch should be from one wire. Headlights always have voltage, it is the job of the limit switch in the headlight motor to stop the flow of current. So the headlight switch (to the motors) does not add power when turned on and remove power when turned off, it simply diverts the voltage to the deploy wire when turned on and diverts the voltage to the retract wire when turned off.
Take some time to read throught those threads and it will hit you.
When the motor shaft pushes one switch open it closes the other. Look at the yellow sheet of paper and see if you have those voltages.
Last edited by Vets-Vet; Feb 17, 2024 at 03:27 PM.
Rig up up an 1157 bulb or use a test light, there are 2 other relays in this network that can be bad and a DVM can be fooled by low current (burnt / dirty contacts).
The headlight switch activates the 2 headlight motor relays. But the motors have to be switched internally for them to move.
Do you have +12vdc at on the grn wires at the motor when the switch is in the on position ??
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Last edited by Vets-Vet; Feb 18, 2024 at 08:53 AM.
The headlight switch activates the 2 headlight motor relays. But the motors have to be switched internally for them to move.
Do you have +12vdc at on the grn wires at the motor when the switch is in the on position ??
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I do not have 12v I have around -3volts. Sorry to get tock so late. Just replaced the switch but the problem persists
In this thread there is a yellow piece of paper with voltages, it is divided into 4 parts, the left side headlight switch on and switch off and the right side headlight switch on and switch off. Each one with three pins. For example, with the light switch off, the left headlight connector on the car side ( coming from the headlight switch) should have 12volts on grey, not much of anything on white, and ground on green. Test them with your meter on the car frame or ground somewhere, not to each other in case you have a bad ground. Also, using ohms (resistance) test the ground.
as you proceed across the yellow paper you will next check the left headlight switch on, then right headlight switch off, then right headlight switch on.
You say you have -3 volts (you did not say where) that sounds like nothing, just floating voltage. Did you rig up an 1157 or 1156 lightbulb to test for voltage ?? Using this for example with the bulb to grey and green headlight switch off left hand headlight, the bulb should light.
The schematic is there, you have to follow it, find where you do and don't have voltage and you will solve it.
There are 3 relays in the left front wheel well, find them in the schematic and test for voltage there.
Last edited by Vets-Vet; Mar 30, 2024 at 09:07 AM.
Find this (below schematic) relay in the left front wheel well and see if you have voltage and ground out of and into the relay. 2 relays will look the same and one is different (isolation), the 2 (like) relays are the ones you want. 1 is the Left headlight (GRN) and one is the right (GRN/WHT). Do your fog lights work ?? Do your headlights light ?? If they are OEM relays they may be bad, they can however be gently disassembled and the contacts cleaned if carbon is the problem. If your readings are correct and ground is switching between green and white (headlight switch off / on), the relays are switching. That would mean either the relay contacts for the green wires are bad or the voltage coming from the 2 fusible links or feeding the 2 fusible links is missing or both fusible links are bad (unlikely). The voltage going into the relay is the key thing to check, light switch on. Also important is the reason I showed the bulb. Digital voltmeters need a tiny tiny amount of current to register voltages where as motors need a large amount. Find 12 volts at the relay first but remember, the 1157 bulb draws about 3 amps and test the circuit for a much higher load than a digital meter. That is why I use the bulb occaisionally.
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You have this and are missing 12V on green / lights on.
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Last edited by Vets-Vet; Mar 31, 2024 at 09:50 AM.
I took a look at the relays and they are filthy. I'm going to order some new connectors and clean the relays themselves. I will post the results after I get this finished
Jose I think you would be better off looking at voltages. Those things have nasty looking old stuff in them from the factory that have turned hard but generally is not the problem. I cleaned mine with acetone.
Jose I think you would be better off looking at voltages. Those things have nasty looking old stuff in them from the factory that have turned hard but generally is not the problem. I cleaned mine with acetone.
is there a good way to test the voltage on them? I put my probes into the terminals but didn't get any reading so I figured it was just dirty but I may not have made any contact
The voltages on the yellow sheet (your white sheet) come from the relays, look at the schematic and match the yellow sheets wire colors to the relay on the schematic. Your problem was the green wires. At some poiint you have to turn into a tech.
Update: went through and checked my voltages and this is what I found.
when off left and right relay voltages:
yellow is ground red is +12v
When on
black is ground. Yellow is +11.5v and red is +12v
isolation relay:
When off yellow and black is ground gray is +12.5v
When on black is ground and yellow is +12.5 v
The voltages on the yellow sheet (your white sheet) come from the relays, look at the schematic and match the yellow sheets wire colors to the relay on the schematic. Your problem was the green wires. At some poiint you have to turn into a tech.
judging on what I can read from the printout, my relays are getting the correct voltages right? So bad relays?
The voltages seem correct as long as they carry enough current to run the motors. If these are original relays the covers can be taken off and the contacts cleaned and very very lightly filed with a fine file or 800 grit paper and cleaned again after. The problem with some relays was the motor malfunctioned and the limit switches (inside the motor) did not turn the motor off after it hit the stops and the motor would have high current. In that situation the little glass bulb inside the motor which is a thermal circuit breaker would open the circuit. Every 7 seconds the thermal breaker would cool off, close the contacts and start the cycle all over again. That cycling is what burned out a lot of relays.
P.S. These motors are strong, once you start fixing things and applying voltages make sure your arms, elbows and hands are out of the way in case the headlight door moves. They are quick when they do so. If you plug a motor in just remember this, Headlight motors always have power, even without the key on. If a headlight is open and you plug in the headlights with the headlight switch in the off position, the headlight will move to the closed position without anything in the car on. Same if the headlight switch is on and motor unplugged it will open when plugged in.
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Last edited by Vets-Vet; Apr 23, 2024 at 09:31 AM.
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1987 Headlights
