Driver's side door lock

Ok...maybe you all can help me figure this out. I've got an '87 GT with power door locks. The locks work, but the driver's side won't unlock. Any reason why? And how I can fix it without takin' to the dealer? Could I fix it on my own? Thanks for any advice in advance.
 
One can grab the lock harness connector at the top of the driver kick panel and probe the wires and note values. The primary color on the lock wires on your 87 should be pink.

Good luck.
 
Follow this link to fix your door lock actuator problems http://jrichker.stangnet.com/Mustang_tech/door_actuator_fix/1_of_8_door_actuator.htm

Stuck with door lock actuators that don't work and don't want to pay the $50+ for a new one? Tried the junkyard ones and found that they last six months and freeze up?

A new actuator for less than $4. Fix one side for $17, do both sides for only $23. I don't sell parts, I don’t make any money off of the upgrade, I just tell you how to do it cheaply and easily.