85SE V6 Headlight Problems

[Fierofool]

85SE V6 Generation 1 headlights. 

The left headlight works properly.  The right headlight comes up but won't go down.  I have more than a half dozen Isolation relays.  All of them have been tried with the same result.  I have swapped motor relays and the problem doesn't go with the motor relay.  I've installed different relays and even bought a new relay.  Same result.

I have close to a dozen limiter switch/brush sets.  I have tried about half of them.  Same result.

I have taken the internals of the motor out and substituted internals from two different motors.  Same result.

The motor has power going to it for the UP movement.  The single blue wire which is the power for the DOWN movement has 12V. 

The light switch has been swapped for two other light switches.  Same result. 

If it has power for the UP and works in that direction and has power for the DOWN but doesn't work in that direction, what can it be? 

[GTRS Fiero]

Have you tried a test ground?

Perhaps a test headlight motor?

When troubleshooting, I test each piece separately.  First, test the functionality of yhe morot by applying voltage, with nothing else.  Detatch the motor from the lift assembly.  Just connect it to a battery.  If that works, try with the motor connected to the lift.  Slowly add in each piece, until it fails.

[Fierofool]

If it has a ground for the UP, it should be good for the DOWN unless it has a separate ground.  Everything in the right side circuit has been replaced with at least one of each component, including the motor.  Light switch, isolation relay, motor relay, motor limiter switch, and the motor itself. 

[GTRS Fiero]

But the question is, does it all work?

[Fierofool]

Well, at the moment, no. 

[TopNotch]

If it has a ground for the UP, it should be good for the DOWN unless it has a separate ground.

Ground is supplied through the headlight relay, and yes, there is a separate path for up and down ground. If the contacts supplying the down ground are bad, the headlight won't go down. The wire marked with the green minus is grounded to lower the headlight door. The wire marked GRY below it is grounded to raise the headlight door.

[GTRS Fiero]

Any luck?

[TopNotch]

If you would like to check with a meter, assuming the colors on the diagram are correct, here is what you should read.

While the headlight doors are going up...
The white wire (WHT) should be open (neither hot nor gounded).
The green wire (GRN) should be hot (+12V).
The grey wire (GRY) should be grounded.

While the headlight doors are going down...
The white wire should be hot (+12V).
The green wire should be grounded.
The grey wire should be open.

Actually, the open wire won't really be open until the limit switch hits. While the door is actually moving, it may be grounded.