: Power Door Lock Repair



Mud
07-17-07, 08:36 AM
Slowly working through mechanical and electrical maintenance and repairs on my 86 FB, time to look at the non-operating power door locks.

I've got a factory service manual coming from ebay so hopefully I should have some wiring diagrams to look at, but hope you can help with some general questions.

All door locks are dead, so I doubt that all 4 lock solenoids are out, hopefully can avoid having to remove any door panels. Nothing happens when you try either driver/passenger lock switches so I am looking for power and/or relay issues. In addition, nothing happens when gearshift is moved from Park to Drive (auto locks?).

I checked the driver side switch - has black, light blue, and orange wiring. Orange has 12v constant, light blue has 12v when switch pushed to LOCK, black has 12v when switch pushed to UNLOCK. So, there is voltage to the door switch, but nothing is happening.

Does this car have the auto lock/unlock when the gearshift selector is moved from Park to Drive?
Is there a location for power lock relay(s)? I looked at, around, and above the fusebox and relay center under the dash but could not find anything.

I do not know if this is related but the power seats were not working either. The drivers side switch had no voltage feed (orange/black wire) - when I ran a temporary 12v feed to the switch, the seats worked fine. I could not track the feed source for this and will probably install a new power feed with circuit break protection to the door switch.

Mud
07-17-07, 11:15 AM
Factory service manual got here - worth its weight in gold. Highly recommend that if you don't have one for your car to get one. Mine ran all of $20 or so.

Already able to see what's going in regards to wiring, relays, and power sourcing. Looks like primary door lock relay is first thing to check, also told me where it is - passenger side footwell.

I love this stuff.

Mud
07-17-07, 12:21 PM
Just following this thread through a bit in case there are others that eventually get faced with this situation.

Found that door lock relay and power seat main switch are powered through the Horn circuit breaker located in main fuse block. That's why I could not find anything related to seats/locks anywhere on any fuse/relay blocks.

The lock switches themselves only need minimal amperage to activate the door lock relay so they are powered from a 20 amp Body Fuse in the fuse block - this fuse is good so that's why there was power to the switches as noted above.

Since neither the seats or the locks work, very good possibility that the Horn circuit breaker is fubar'd. Come to think of it, I have never honked the horn, so I am assuming that it may not work as well.

FASSTWOOD
07-18-07, 12:04 AM
I thought the seats had a circuit breaker in the fuse box?

Mud
07-18-07, 07:30 AM
Not in my car.

As mentioned, primary power to the main seat switch (drivers side switch assembly) and the power locks comes through the terminal labeled Horn Circuit Breaker. There is NO terminal labeled Power Seats or Power Locks.

There are two feed wire terminals on that fuse block - one on the left and one just below the horn circuit breaker. These are the feeds for the power seats and the locks and they are not labeled.

The power seat motors and the power lock solenoids each have a built in non-serviceable circuit-breaker for individual protection as well.

96BIG_BODY
07-18-07, 12:54 PM
i just made a topic about similar issues, but MUD you said the horn circuit braker powers the door locks and power seat? on the 81 we have the door locks dont work and the drivers seat tilt dont work but the horn does:confused:

Mud
07-23-07, 09:47 AM
Here is the latest for the win.

The horn DOES work, plus I checked the fuse terminal so the horn circuit breaker was OK after all. The wire feed at the fusebox has 12v, but there was no voltage at the driver door switch, so there was a problem between the 2 location.

Service manual showed 2 factory splices in the circuit that feed both the power seats and the power lock relay. Problem is that the splices are both in the harness that is inside of the drivers door. You have to remove the door panel.

I removed the panel and found the first splice - no voltage. I ran a jumper from the battery to the splice crimp and voila! seats and locks worked like a charm. Incidentally, the passenger side power seat feeds through the driver side door switch.

So that told me that the other splice may be the problem, or there is a break in the wire where it comes through the door jamb. I am inclined to think that it is a wire break issue, as the harness seems to be very intact inside of the door. Easy fix now to simply trace about 18" of wire from the door back to the fuse box or to simply add a new section of wire.