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Rear door lock on wagon not unlocking/locking

16K views 9 replies 4 participants last post by  smt029 
#1 ·
Lock question-

I have a 2000 Mercury Sable wagon. Just this weekend the rear door lock stopped locking/unlocking with the remote. The key doesn't seem to work either, or it's just really hard to turn (I haven't tried to force it). Essentially to unlock the rear door I have to climb into the back seat and reach way back for the lock. At least I can lock it by swinging open the window in the back.

Funny thing is about a year ago it did that once or twice but started working again. This time it doesn't seem to be coming back.

Is the lock most likely broken and I need to take it somewhere to get it repaired, or is there something I can try to do to get it going again?
 
#2 ·
If all your other door locks are working it's most likely the wiring harness between the roof and rear hatch. There is a rubber boot that protects the harness between the roof and hatch but the wires inside become brittle over time and eventually crack. To repair mine I pulled the boot out of the roof side and cut it with a razor a few inches and rolled it up to expose the broken wires, stripped the insulation off the broken wires, and then used some crimp connectors on them. I had three broken wires altogether. Put the boot back and wrapped some electrical tape on it. Has worked fine ever since. Good luck!
 
#3 ·
Yes all the other locks are still working - I'll check the wires in the back. Thanks!

If all your other door locks are working it's most likely the wiring harness between the roof and rear hatch. There is a rubber boot that protects the harness between the roof and hatch but the wires inside become brittle over time and eventually crack. To repair mine I pulled the boot out of the roof side and cut it with a razor a few inches and rolled it up to expose the broken wires, stripped the insulation off the broken wires, and then used some crimp connectors on them. I had three broken wires altogether. Put the boot back and wrapped some electrical tape on it. Has worked fine ever since. Good luck!
 
#5 ·
The electric motors for unlocking the doors are childs toy grade motors. This is where your problem is.

They almost always fail eventually. I have seen pictures of them and usually they get wet and rust/lock up. You can swap internals from another Ford vehicle that will fit, i remember somewhere back a thread where they found a more reliable setup that would fit in there but not sure which vehicle it is.
 
#6 ·
When I was working on this problem I found that my mechanical hatch lock also worked very poorly, but it was due to lack of use more than anything. It was gunked up with dirt and dust from always using the electronic actuators. When the actuator stopped working I found the mechanical lock to be very problematic until it got regular use and then it was Ok.

Before he takes his rear hatch panels apart it's easier to check to boot since it's already exposed between the door and hatch. The actuator is likely still good if none of the other actuators have failed.
 
#8 ·
Well it's working... It turned out to be a really technical solution:

I sat in the back of the car scratching my head and playing with the lock (locking it and unlocking it for a few minutes thinking 'where are the wires I need to mess with?'. I closed the door and the door is locking/unlocking again with the remote (for now)
 
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