I am doing a complete rewiring of an 84 for racing purposes but the class requires the headlights to function as it normally would in a stock/street scenario. We swapped out the original three wire motors to the later two wire in addition to replacing the three relay bank with the later controller found in a junk yard. I have also attached a screen cap of the new wiring schematics as installed now.The headlamp control module mounts under the passenger side headlight. With the headlights open you should unplug the motor from the vehicle so it can not close on you. Then remove the plastic bezel from the open RH headlamp assembly and you will be able to see and reach down below the headlamp to the control module. It is a small black plastic piece with 2 plugs going to it. This is the relay that sends power to the motors and sends reverse polarity to close. This is likely your failure. Don't forget to inspect the 2 connectors for water intrusion or expanded pins.
Of the wires running to these 2 connectors..
Black is ground. It needs to be grounded at all times
Orange is power There are 2 of these wires that run to separate fuses in the underhood fuse block and get power all the time
White is the headlamp on signal This should get power only when the headlamps are commanded on
Dark Green is the headlamp off signal This should get power only when the headlight switch is in the off position
Those wires are all in connector C1 and connector C2 has the pair of green wires and the pair of blue wires that go to each headlamp motor. If you are having a problem getting power to the white or green wires when the headlamp switch is in a given state then you obviously have a headlamp switch or BCM/ambient light sensor failure as the BCM can command the headlights on and off with the Twilight Sentinel. If when the headlamps are switched off you have no power on the white wire and power on the dk green wire and power on both orange wires and ground on the black wire then you likely have a failed headlamp control module.
One final test you can perform is to use the knob on each headlight motor to manually run each motor down to the half way position and then retest the operation. There are switches in the motors that break contacts when the motor hits it's point of load/stop and while both failing together would be rather rare, this is an important verification step if we want to make sure we look smart and ensure that we only replace one part to correct the failure.
The entire dash has been replaced with a formed sheet metal replica and the original digital dash has been removed and replaced with analog gauges and all Honeywell NT MIL-SPEC style toggles.
The doors will open but they will not close and I suspect the control module as all the input voltages and switching are correct as per the factory schematic but it is the outputs from the four pin connector to the motors that I see what I consider a problem. When I have the switch in one position or the other, one of the wires for each motor shows a solid 12VDC but the other one shows a voltage of about 11.4VDC and I was expecting to see 0.
To me it seems the internal solid state coil/switch is not functioning correctly. We did have another controller bought at the same time from the same yard and it does exactly the same.