I've got headlight problems w/ my 86.
The right headlight won't go up. This happened last year to the left one and replacing the motor solved the problem...
I've replaced the motor and the actuator & still the problem exists.
Should I replace the isolator also ???
Pls help thx ...
Pete

 

Mounted at the front of the driverside plastic wheel well housing are 3 relays. Two of them are the same. The one that is different is the Isolation Relay. It's only used to close the RH Headlight bucket.

The relay socket for the RH motor has 5 wires going to it.
Red, Yellow, Black, White Black and Dark Green/White.

The relay socket for the LH motor has 5 wires going to it.
Red, Yellow, Black, White and Dark Green.

The Isolation relay has 4 wires
Yellow, Gray, Black and Red.

With the RH headlight motor in the fully closed position do the following.

Disconnect the electrical plug at the motor. There are 3 wires at the plug. Red, Dark Green/White and a White/Black wire.

At the plug going into the motor, use an ohm meter and you should measure a couple of ohms from the Dark Green/White wire and the White/Black wire. If you don't something is wrong with the motor . Could be worn out brushes or one of the two mechanical limit switches is misadjusted.

If you do measure low resistance the RH relay is probably bad.
Swap the door relays around and see if the RH motor opens.

 

Check the relays, wiring, and connection too them.

 

On my 86 it was a bad ground at the 3 wire connection at the motor. Replaced the watertight connector & presto it works.
Best of luck. I love electrical problems (not).
Larry

 

Unplug the RH motor and jump 12 v (grn + and wh -) and the headlight door should open. If it doesn't then your problems are in the motor. Down, jump 12v (red + and grn -) . Swap the RH and LH relay and observe if the problem follows the relay.

 

Hooked on Vettes,
Thx for your reply. I tested the motor it works fine. Additionally I swapped the actuator relays and the same problem occurs so it's not the actuator relay... Are you sure the Isolation relay only operates the closing of the RH headlight and not the opening also... That was my next option was to change out the isolation relay.
Pete

 

JFB,
Thx for the reply. I tried your suggestions and the motor works fine. I swapped the relay and the problem doesn't follow the relay. The RH headlight still doesn't work. What do you know about the isolation relay ? What does it do ???
Thx Pete

 

http://members.shaw.ca/dankai/Headlight%20Doors.pdf

 

Thx for the schematic Agent 86 ...
Pete

 

If you want to eliminate the Isolation relay from causing the RH motor to not open the headlight door, pull out the relay.

With the relayout the RH headlight door will not close does. It should open but not close.

Pull the Headlight switch to the on position and see if the RH door opens.

If that doesn't resolve the problem which I don't think it will, do the following..

Remove the RH Motor Relay.

Verify you have 12 volts on the Red wire at the socket. This wire is hot at all times and supplies the 12 volts to open the RH motor. It's a fusible link. There are two fusible links one for each motor.

When the motors are told to close, the Light Switch supplies the 12 volts.

 

The RH door relay supplies +12v to the green wire and ground to the wh/blk wire to make the motor open the door. Unplug the motor and turn the headlights on, then measure if you have +12v on the green wire and with your ohmeter, confirm that the wh/blk wire has low resistance to ground. If neither, then measure if you have +12v on the red wire on the relay socket and also have +12v on the yellow wire on the relay socket. The red wire goes to the battery through a fusible link and the yellow wire, the headlight switch provides +12v to operate the relay coil to open the door. The black wire on the relay socket goes to ground and you should check with an ohmeter that the black wire has low resistance to ground ( or the neg battery terminal).

 

Sorry in my last post I was thinking the LH motor wasn't opening.

I corrected the post. If you swapped the relay the only thing left is the wiring or no 12 volts from the fusible link on the red wire.

Are you saying the RH door does close?

If it does the ground must be good because the same ground is used to open or close the door and energize the RH relay.

 

JFB,
Thx for the quick reply. Your guidence and knowledge helped find the problem. I was able to track down a faulty fusible link (due to battery corrision) coming from the relay to the battery. The relay had low voltage going to it. From your email I was able to track this down... I would have never figured that one out w/o your help...
Thx again...

 

HOV,
Thx for the quick reply. Another response helped me track down a faulty fusible link (due to battery corrision) coming from the relay to the battery. The relay had low voltage going to it. You were on the right track - it was low voltage, due to a bad fusible link.. I would have never figured that one out w/o help from you guys...
Thx again...

 

There is a rubber hose that drains the cowl area and dumps any water right over that fusible link jumper block.

If you use a small piece of heater hose, you can extend the drain hose and divert the water away from that area. Here's a pic. of mine.