Headlamp motor

Thanks Bernice. With my limited capacity of understanding anything with a max of 2 wires, your instructions were perfect for me. I tested 7 different motors and 6 were working fine. The other is in the trashnow. I knew you were looking for some spares, but shipping from Montreal to California is probably more than the value of a new headlamp motor. Now the diodes... tomorrow evening. At least I see some progress now!
 
If the motors pass the previously outlined test, they are likely good. To test the diodes, simply reverse the power, the motors should not run if the diodes are good. Diode test with a meter is not the same as testing them under actual operating conditions. The diodes are there to prevent the two motors from interacting and if one of them fails (usually open circuit) the motor does not run during one of it's cycles (up or down). If the diode failure is a short, the motors can interact in wierd ways.

If the motors are good, test and verify the relays, switch and wiring is GOOD. If needed, can write up a test procedure to check this.


Bernice
 
OK. Maybe I misunderstood. 6 motors running fine after testing like suggested. Step 2: To test the diodes, I did the reverse: I put the power on the ground and the negative on the green wires. All 6 motors ran again. Does that mean I got it wrong or does that mean I got 6 motors with bad diodes?

Could find a clear pic of the diodes and wires where they enter in the headlamp.So I took a pic of one of my motor if needed to refer to some wires.

20190214_204738.jpg
 
Just out of curiosity, I found some headlamp motors have their diodes cleverly hidden. The picture in my previous post was from a 1500cc headlamp motor. The next one show, side by side what I believe is an early 1974 (bottom) while the other (top) is the common one from the 1300cc.
Even then, you could notice the cleaner wiring arrangment of the 1300 vs the 1500.

20190305_150628.jpg
 
Following Bjorn suggestion, I tested my diodes and found ALL my spares were bad (7). And the one I was trying to fix, I put one diode backward. So I fixed that. Tested the diodes and everything seems right. So I wired everything to the car (but not bolted in place).

Now the left headlamp didn't raise and the motor kept turning after I close the headlights. (It was the reverse before that). I had to cut the ignition to stop it. So, is it something like the motor has to be in place and will stop when hitting the adjustment bump. And then the raising will be possible?

This is not related to the other side since I unplugged it. Or is it something about the headlamp switch?

It's been more than 2 months that I'm trying to fix that!

In 2 more month, my 1987 Bertone will be accessible (now under a tarp covered with a couple of feet of ice and snow), It has good working headlamp, so I may be able to swap them to be sure what is the problem (motors, wiring or switch).
 
The switch contacts on the big gear (under the diodes) control the motor power on and off; when it reaches the park position it should open a contact and stop, installed or not.

The motors only run one direction, half a turn up then an additional half turn down (At the gear, not the motor itself) when turned off.

If you have a meter, you can check the contacts working by monitoring the wires and using the hand knob to rotate the assembly.

My car had a bad contact; it was repairable.
 
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So I've been working on the headlight motors on and off for a while and the headlights didn't lower intermittently. The headlight motors worked most of the time but when they would fail, a slight tap on the fuse panel would make them lower.

Finally the headlights stopped lowering permanently so I thought I'd have a better shot at troubleshooting the problem. After reading the post by ng-randolph I gained a much better understanding about how the motors work and which wires provide the up and down signals. I found that fuse 11 and the tabs that hold it in place, needed a better connection. The fuses appeared a bit loose. After cleaning the light corrosion on the fuses and holders, and tightening the connection between the tabs and the fuses; the headlights worked correctly and consistently. Thanks for sharing that great explanation, it brought me to a solution.

Tommy
 
ng_randolph said:
I found the wire colors in the 1980 Electrical Troubleshooting Guide. Each motor should have 5 wires coming out:

  1. A lonely black wire that is the ground connection for the motor.
  2. A solid green wire ending up in a 2-pin connector. This is the +12V connection for the motor.
  3. A green wire with a black stripe. This is the "down" signal, and the wire ends up in the same 2-pin connector as #2 above.
  4. A Grey wire that ends up in another 2-pin connector. This is the "up" signal.
  5. A black wire that ends op in the same 2-pin connector as #4 above. This is the common signal.
Turn the knob on the back of the motor to set the headlight somewhere between fully closed and fully open. Get out your multimeter (and if you don't have one, best $10 you'll ever spend) and set it to diode test (if available, or continuity test otherwise). Put the red probe to the GRN/BLK (#3 above) and the black probe to BLK (#5 above). On diode test you should see something around 0.7V, and on continuity test you should see continuity. Now switch the red and black probes. You should see no continuity, and diode test should read infinite.

Then put the red probe to GRY (#4 above) and the black probe to BLK (#5 above). Again, on diode test you should see something around 0.7V, and on continuity test you should see continuity. Now switch the red and black probes. You should see no continuity, and diode test should read infinite.
Click to expand...
Thank you for this write-up, it is pure gold!

Tommy
 
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