Headlight control module fix – third generation f-body message boards electricity kwh usage calculator

The 87 was the initial project. When we had difficulty with the headlights, and traced it to the module, we found that rapping the module would get it to work, but only temporarily. Sooner or later, it would stop working properly. So, we swapped in the module from the 88, and all problems disappeared.

I am now researching parts and other info for restoring the 88, and I learned to my horror that it is nearly impossible to find this part new, and if you can find it, it is a $300 part. Now it is possible to obtain the module as a used part; there’s a place that refurbishes them and sells them for $60.

In addition to the risks associated with buying such a part used, I am sure that supply will dry up eventually… that’s why I decided to try and fabricate a replacement. After looking at the repair manual schematic, I reasoned that it would likely be simple enough to just build something with the necessary relay(s) to replace the OEM part. I’m sure that some would regard this as a ‘hack job’, and it would not please the judges at car shows… AND…

SO, I decided to open up the defective module, as it seemed to be a matter of prying with a screwdriver. The case opened with little difficulty. Inside, I found a circuit board, with chips, diodes, and a couple of transistors. This is evidently the logic circuitry that does all the decision making. There is a single relay in the center of the board, and this is the part that reverses polarity, on command from the board.

There is some heat warpage on the clear plastic cover on the relay. Owing to the fact that tapping the module with a screwdriver handle would get things working, I am assuming that the relay, which is the only moving part, is what has failed here.

The relay is made by Omron, and the part # is MY4-02-US 12VDC. I have only found it at one source: California Radios Plus, $13 plus $7 shipping. There is a replacement part made by Omron that is sold by many, including Mouser Electronics, and it is cheaper than the original part. The problem is that it has flat terminals on it, and the original has pins that are soldered to the circuit board. I assume that if you were a patient sort, you could modify the relay and/or the board to accept the replacement, which is only $6 plus shipping. The reason I mention this is because it appears that eventually Cal Radios will likely run out of their stock, which I assume they cannot replenish.

I decided to take another look at my problem a few hours ago. Called my brother who is a mechanic asking about fuses for the headlights. He pulls up info about the Convenience Center under the dash right of the steering wheel. Should be two fuses with orange wires going to each. One fuse for each headlight. To help locate the Convenience Center he said to turn on the hazard lights and track down the clicking sound under the dash. The fuses should be right around the clicking sound. To do a quick check on the fuses he said I could take my voltmeter and check the volts on the orange wires on the headlight module.

Now I did the wire jump from the pigtail to the module and my headlight did come up. So apparently I need a new module. I checked it over a few weeks ago and everything looked fine and dandy. So if someone could enlighten me how to repair one please post something up. I even went through and resoldered both connecters on the circuit board with no help.

I did try to check the volts on the orange, key on, headlights on, plugged in the red probe into one of the orange wires, and then touched a good to my knowledge ground with the black probe. All I got was either 0.00, 0.01, or rarely 0.02. I have no idea about how to use a voltmeter so if I did it wrong someone please tell me the right way.