Finding/fixing broken driver door lock wire

[FrugalGuy]

1999 Ford Explorer XLT v6
Electric driver's door lock (left hand drive in the US) does not lock and does not unlock driver's door. The button DOES lock/unlock all other doors and the hatch.
Previous "repair" shop appears to have removed and binned the lock actuator (!) so I've bought a new one and tested it with a 12V supply -- the actuator is good.
Getting zero voltage on the LH actuator connector (Pink w/Black stripe and Red w/Orange stripe) when I press Lock or Unlock.
Passenger door shows +10V or -10V on the passenger (RH) connector for lock/unlock, so I know it's a wire problem.

Located wire bundle at door sill of driver's door. Punctured the Pnk/Blk and Red/Org wires found there and confirmed that when the door lock button is held down for LOCK, I see +10V on the wire pair (so break is between driver's door sill and connector).
Oddly, when button is held down for UNLOCK, I see only 0.44V on the wire pair (should be -10V). Could it be that the short closer to the connector is causing the 0.44V reading without interfering with the 10V reading?

Big question: Should I / How do I open that big black can on the driver's door hinge in a way that I can seal it back again?

I've got to find the break and repair it. If I can get that rubber sheet under the driver's kick plate, I guess I can take another reading just before the wires go to the door.

 

[C420sailor]

Corroded splices in those wires. Ford uses these crap splices that corrode.

Follow the wire through the harness and you’ll find thicker portions about 1-1.5” long under the insulation. Cut them open and you’ll see what I mean. Splicing and soldering in wire in place of those splices will get your voltage way up.

 

[FrugalGuy]

Thanks. Is there any way to know if I should look closer to the relay in the cargo area or closer to the door jamb?

 

[J_C]

At first I was wondering why you were testing what is probably the wire pair running to the rear door, since Ford used (almost) the same wire colors to all 4 door lock actuators, then I remembered that most trim levels including XLT, probably have the keyfob remote unlock feature, so at least one of the wires (red/orange) is coming from a relay in the box next to the rap module (pictured below) in the left rear quarter panel behind the trim, while the pink/black wire might be going to a different door. See attached wiring diagram. All the pink black wires for all doors are electrically in common with each other and it's the red/orange or pink/orange that is switched on and the polarity to actuate each door lock.

What I would do next is measure resistance between the driver's door lock connector pink/black and the pink/black in the bundle pictured. If you have low resistance, then the pink/black to the driver's door is probably intact, but more thorough would be measure resistance between driver's door pink/black and any other door (that still works) actuator connector pink/black, or between driver's door actuator pink/black and door lock relay contact #30.

Still assuming that you have the remote keyfob unlock feature, then I would use a multimeter to measure resistance between the red/orange wire and the Driver's Door Unlock Relay contact #3. If you have low resistance there, then it seems both of the wire runs are intact.

If they are both intact, or maybe go ahead and do it now since it's easy, swap the driver's door relay for another of same type to see if the relay is bad, like the trailer tow park relay right next to it (if present, if not then one of the other relay boxes should have this same relay type). If all of that checks out, then I'd start probing for power getting to the relays.

On the other hand when checking resistance between the two groups of points mentioned above, if it is open circuit then I would cut the wire at both ends and string a new wire between those two points, again making sure you have the right wire since the pink/black go to every door and even the liftgate, and the red/orange could look similar to a pink/orange with a low CRI, high color temperature LED flashlight.