This issue is probably uncommon, but I’ll make a quick mention of it since we found the problem.

On our 1998 Ford Windstar, we had a weird issue with our power door locks. When pressing the lock button on either side of the front doors, the door locks would sometimes fail to lock. However, if you press the lock button located by the tailgate, the doors would lock 100% of the time.

A forum on the internet stated that the tailgate lock switch was located on a different circuit using a separate relay. It also stated to look for some wires by the driver’s side door that were spliced into the main wire harness. It claimed that the splices corrode over time, breaking the connection. My dad and I found the spliced wires, but the connections were ok.

My dad made a comment to look behind the passenger’s side kick panel. About that time, my mom came out to check on our progress and sat in the rear seat. While I was checking the wires that were behind the kick panel, my mom shouted “What did you do?” She said the dome light by the sliding door was flickering on and off.

Turns out that there was a wire harness coupler plug behind that kick panel that wasn’t fully seated in place. Either it wiggled loose over time or was never fully seated during assembly. If the kick panel was bumped correctly, the connection for the locks was either made or broken. Since we reseated the plug, the door locks have since successfully locked.