door locks quit working after changing heater core....help!!

BKM48198

5 Year Member
Jun 7, 2008
373
28
49
Ypsilanti, Michigan
I installed a new heater core over the weekend and now the power locks don't work, I unhooked the wiring under the pass. side kick panel and re-hooked everything I think, I do have an alarm system which connects under the drivers side kick panel and I could have damaged a wire there also since that kick panel was off too but the alarm works fine, it just won't work the door locks now. I have a wiring diagram but dont know the best way to start checking the wiring, should I go from the switch on one door to the other or is there a better way? Any recommendations would be appreciated, I have a digital volt/ohm meter but am not the best with electrical issues. I did try swapping out the 20A circuit breaker in the fuse panel but havent dont anything else other than look for a broken wire or loose connection with no luck, anyone had this happen to them before ?
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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There's a small wiring harness that runs along the firewall top from the drivers side to the pass side. Check to see that it is plugged in on both side. It's a small gray connector on each side.

Would help to know what year as the wiring did change depending on teh year
 

BKM48198

5 Year Member
Jun 7, 2008
373
28
49
Ypsilanti, Michigan
There's a small wiring harness that runs along the firewall top from the drivers side to the pass side. Check to see that it is plugged in on both side. It's a small gray connector on each side.

Would help to know what year as the wiring did change depending on teh year
Car is a 1990 GT, what does the connector look like and how many wires and what color wires would be in it? I just put a 347 in it and must have damaged the heater core during the swap, everything else works as it should other than the power locks. I have heat now and still am working on the break in oil and just want to enjoy the car with everything working.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
36,934
12,800
224
Massachusetts
I don't know the wire number, but the colors for the locks are : Black/white, Pink/Light Green and Pink/Yellow. There is also a Pink/Orange and Pink/Black wire that runs across to feed the opposite side door lock actuator. basically you are looking for a bundle of at least 4 pink wires.

Here is the wiring diagram. You should have voltage at the Black/WHite wire on both sides. You can see that the wiring is set up to run in series so that activating one lock will trigger both door locks.

C601 and C501 are inside each door. C221 and C222 are in both kick panels. The pink wires should make it easy to spot. My bet is one of these two connectors is not connected. According to my FSM they are gray in color and it shows it's an 8-pin connector.

The grounds (G500) are inside the driver's door.

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