Driveside Headlight will not open
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Intermediate
Joined: Jan 2010
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Driveside Headlight will not open
On my 87 the driverside light just stopped opening. I manually opened the light and turned the lights on. When I turned them off they both closed but when i turned back on it would not open. I tried switching relays and still no luck. I am assuming the motor is good since it closed with no issues. What could be the problem?????
Advanced
Joined: Aug 2007
Posts: 83
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From: Cambridge Ohio
I'm having the same problem on my 87. My pass. side will open but not close, swapped relays, same result. Swapped left and right units, right works fine on left side, left has same problem when hooked up to right side. Does anyone have a wiring schematic from the FSM?
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The 87 uses three relays to operate the headlamp motors. Each motor has it's own relay and a 3rd relay called an isolation relay. That relay changes the current polarity for the motors to open and close the headlamps. Changing the polarity makes the motors run in either direction.
One thing to check for is the wire harness terminals. Sometimes the wires will pull loose from the terminal socket and current won't flow to the relay terminal. GM used a black gooey waterproofing and sometimes it will harden and the wire will pull from the socket.
If the wires aren't the problem, replace the isolation relay and it should fix the problem.
Part numbers:
Headlamp relay: AC Delco D1784 GM 10031018
Isolation relay: AC Delco 15-2386 GM 10039961
They should be available at a store that sells AC-Delco parts. About $17 each.
One thing to check for is the wire harness terminals. Sometimes the wires will pull loose from the terminal socket and current won't flow to the relay terminal. GM used a black gooey waterproofing and sometimes it will harden and the wire will pull from the socket.
If the wires aren't the problem, replace the isolation relay and it should fix the problem.
Part numbers:
Headlamp relay: AC Delco D1784 GM 10031018
Isolation relay: AC Delco 15-2386 GM 10039961
They should be available at a store that sells AC-Delco parts. About $17 each.
Advanced
Joined: Aug 2007
Posts: 83
Likes: 0
From: Cambridge Ohio
Update
I just got both of mine working! I ohmed out all 3 wires from the relay to the right headlight plug. 2 of them were @ .002 and the red one was @ 1.8 ohms. The left side did not ohm out with any high resistance so I put a jumper wire from the red lead at the relay to the red lead on the headlight plug and it opens and closes! I did not cut the red wire, only stripped enough insulation away to put a jumper clip on. If I disconnect the factory red wire, it won't open, so the red wire is going somewhere other than just the headlight. I've only had the car for a week, gotta get a FSM soon! Hopefully a guru can answer this one!
