87 headlight problems-weird
Thread Starter
Racer
Joined: Feb 2009
Posts: 252
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From: connersville IN
87 headlight problems-weird
The d/s will not turn over.If you use the **** to man. open it it will shut with power.
Whats wrong with it?where do i get the part?new to c-4s,help me out guys
Whats wrong with it?where do i get the part?new to c-4s,help me out guys
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Each headlamp has its own relay that provides power to the motor when the headlamps are turned on. In addition, there is an "isolation relay" that actually changes the motor polarity so when they close, the motors run in reverse. The fact that the motor is moving the headlamp assembly closed means the gears are OK and that the motor works.
The three relays are under a small metal shield in the driver's side headlamp well. The shield is attached to the plastic front fenderwell. You can remove the shield to expose the relays. Note that one is slightly different in size than the other. That's the isolation relay.
If you swap the two relays that are the same size, the other headlamp should have the problem. The relays are not expensive, about $16 each.
Also, the relays have a gummy dielectric grease around the contact blades and after years of use, the grease gets hard and there may be a loss of contact between the blades and the harness connector. Sometimes it's just a matter of cleaning the contacts.
Here's some AC Delco part numbers:
Isolation Relay 15-2386 (only uses one)
Headlamp Relay D1784 (one for each headlamp)
The three relays are under a small metal shield in the driver's side headlamp well. The shield is attached to the plastic front fenderwell. You can remove the shield to expose the relays. Note that one is slightly different in size than the other. That's the isolation relay.
If you swap the two relays that are the same size, the other headlamp should have the problem. The relays are not expensive, about $16 each.
Also, the relays have a gummy dielectric grease around the contact blades and after years of use, the grease gets hard and there may be a loss of contact between the blades and the harness connector. Sometimes it's just a matter of cleaning the contacts.
Here's some AC Delco part numbers:
Isolation Relay 15-2386 (only uses one)
Headlamp Relay D1784 (one for each headlamp)
Melting Slicks
Joined: Mar 2008
Posts: 2,453
Likes: 347
From: SC
My 87 left headlight would work sporadically. Open , not close, sometimes not open...etc. If I turned the **** slightly it would flip. I took it apart figuring it would need gears. After 21 years the gears were remarkably in good shape. What I did find was one of the radiused magnets in the motor housing had broken in half and loose from the metal housing. I assume the magnet was jaming the motor. It did work however. I was able to super glue it back together and epoxy it back in place. So if it is not a relay or gear problem, it might be something to look at. Of course, you would have to take the motor apart to see what is going on inside.
Advanced
Joined: Nov 2008
Posts: 92
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From: Meridian Mississippi
I had the same problem with mine. I put a test light on all of my relays and it showed that they were working fine and when nothing I did helped I bought some new relays and BOOM they worked try that and let me know.
Team Owner
Joined: Jan 2003
Posts: 20,316
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From: Summerland B.C. Canada
Race Director
Joined: Jan 2006
Posts: 10,039
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From: CA
You did say d/s right? Odd, usually it's the p/s that seems to give more trouble.In the d/s door motor there are two limit switches.They ,in simple terms, tell the motors to go forward or reverse. Of course there are other relays involved as stated in above threads. Sometimes the contacts of these get dirty.They are not real easy to get to without taking the whole assy. apart.Try tapping on the motor housing.Believe it ,or not, that sometimes frees the limit switches up.Good luck.
