◀National Parts Depot’s latest Fox Mustang catalog is chock full of ’79-’93 Fox hardware, including everything you’d need to get your power door locks functioning again. With over 800 new products, many of which are for the ’79-’86 “four-eye” Mustang crowd, you’d be surprised what NPD has to help your Fox get back on its feet.
Many of us have grown accustomed to the creature comforts of life. From filtered water through your fridge door and a remote control by your side on the couch to power windows and door locks in just about every vehicle made in the past 20 years (excluding those uber-cheap rental cars we all have to endure now and then). So it can be frustrating when one of these comforts goes belly-up without notice. I mean, who wants to get up off the couch and walk five feet to change the TV station (if you can even find the button on your flat screen!)? Seriously though, when a power window or power door lock system goes on the fritz, it affects not only the security of your Mustang, but yours as well.
1 It’s always best to diagnose...
1 It’s always best to diagnose the concern rather than throw parts at the problem until it’s gone. We begin by removing the switch panel in the passenger door and checking the black wire with white stripe for power. This is the hot-at-all-times wire leading to both door lock switches. As you can see by the test light, we were good here.
2 Next was to test the switch...
2 Next was to test the switch to see if power from the black wire with white stripe was transferring to the pink with orange stripe “lock” wire, which goes to both door lock actuators. Pushing the “lock” side of the switch illuminates the test light. We also tested the “unlock” side of the switch (pink with black stripe), which was also good. This means our issue is farther down the circuit; either a break in the wiring or a bad actuator. Since the driver’s door lock actuator worked (but sluggish), we can rule out a wiring issue.
3 If your test light didn’t...
3 If your test light didn’t illuminate when you pushed the lock or unlock buttons in the previous test, you might have a bad switch. Remove the switch from the panel and bench test it with an ohm meter. Connect one lead to the switch’s center pin and the other to one of the corner pins. You should have an open circuit until you push the switch in one direction, which will then show continuity.
3 If your test light didn’t...
3 If your test light didn’t illuminate when you pushed the lock or unlock buttons in the previous test, you might have a bad switch. Remove the switch from the panel and bench test it with an ohm meter. Connect one lead to the switch’s center pin and the other to one of the corner pins. You should have an open circuit until you push the switch in one direction, which will then show continuity.
4 Getting inside the door...
4 Getting inside the door of your Fox isn’t difficult, only requiring a 3⁄8-inch socket, a Phillips screwdriver, and a door panel tool. Begin by removing the armrest. You’ll find two 3⁄8-inch bolts behind the access plugs (shown here) and a Phillips head screw at each end.
5 Fold the armrest down to...
5 Fold the armrest down to access the wiring connections and carefully disconnect them to remove the armrest. Keep the switch panel nearby, as you’ll be plugging that in for further testing. Finally, remove the Phillips head screws retaining the inside door handle cup and the sail panel at the mirror (one screw each).
Our 22-year-old ’90 hatch has been through a couple of replacement door lock actuators over the years but this time things were different. The driver’s side actuator worked fine, though a little slow from age, whereas the passenger door wouldn’t unlock at all from the driver or passenger lock switch. Often, when the actuator seizes, you can’t even turn the door lock tumbler with the key (and yes, you can break the key off in the lock—we have that T-shirt). So we weren’t 100 percent sure it was the actuator this time. We simply had to tear into the Fox’s door and do some simple voltage and resistance checks to verify the failed part or wiring issue and not simply throw parts at it until it works again.
6 Using a door panel tool,...
6 Using a door panel tool, carefully slip the tool between the panel and the door shell, then use a flashlight to find the door panel clips. Pry the panel away from the door shell at these clips, otherwise you run the risk of tearing them out of the fiberboard. Once you’ve released the clips, simply lift the door panel off of the door shell.
7 You’ll need to pull back...
7 You’ll need to pull back the plastic vapor barrier to access the door lock actuator. Carefully work your way around the plastic’s edge to separate it from the door shell without tearing or stretching it.
8 A peek inside the door and...
8 A peek inside the door and we were greeted with this view, a door lock actuator with a disintegrated weather boot—a sure sign our actuator is seized.
9 Unplug the wiring connector...
9 Unplug the wiring connector from the door lock actuator and use a test light to once again verify power is getting all the way to the end of the circuit by pressing the lock or unlock button to see if the test light illuminates. Our wiring checked out fine.
10 You have a couple of options...
10 You have a couple of options for actuator replacement. You can drill out the retaining rivet in the door and remove the actuator with its plastic bracket (you’ll need a replacement rivet and jumbo rivet gun, or some people use a small nut and bolt to secure the bracket), or you can carefully pry the actuator out of the stock bracket and leave the bracket in place. As you can see in this photo, that is exactly what we did here, and prefer to do. You’ll also notice we removed the anti-tamper cover from the door latch for better access and photos (it simply unsnaps from the back of the latch).
11 As we mentioned in our...
11 As we mentioned in our lead photo, NPD’s Fox Mustang catalog is chock full of hardware to restore and even lightly modify your ’79-’93 Mustang. They offer several door lock actuator options; we picked up their budget model (PN M-218A42-1B, $22.95), which requires installing the proper actuator rod onto the unit (included). Simply slip the rod into the head of the actuator and press the roll pin into place with pliers or a bench vise.
So follow along as we delve into the Fox Mustang’s power door lock wiring, switches, and actuators to see where the problem lies and then you’ll know what to do when (not if) your power door locks go on strike.
12 The actuator’s rod is installed...
12 The actuator’s rod is installed into the door latch by inserting the rod in a horizontal position and then rotating the actuator downward and then up into the mounting bracket. Place a few drops of liquid soap onto the actuator’s rubber mounting bushings and install the new actuator into the original bracket. Don’t forget to reconnect the wiring connection to the actuator and to reinstall the anti-tamper latch cover.
13 Besides the actuator itself,...
13 Besides the actuator itself, NPD offers replacement door lock switches. Be sure to order the correct side, as they are indeed side specific. The special installation rivet, if you opt to drill yours out (or break the bracket during removal of the actuator), as well as new door lock rod retainers and even the door latch itself, are all available from NPD if you get into your door and find other issues.
13 Besides the actuator itself,...
13 Besides the actuator itself, NPD offers replacement door lock switches. Be sure to order the correct side, as they are indeed side specific. The special installation rivet, if you opt to drill yours out (or break the bracket during removal of the actuator), as well as new door lock rod retainers and even the door latch itself, are all available from NPD if you get into your door and find other issues.
Fox Mustang Door Lock Wiring
When diagnosing your door lock issues, you have to understand how the circuit and the switches work. The door lock switches have contacts that are closed when the switches are at rest. This is how the switch can pass through the ground circuit and reverse the polarity to make the actuator move up and down (same concept for your power window switches). The black with white stripe wire feeds power to both of the switches, but the lock and unlock circuits actually start at the driver’s switch and run to the passenger switch and THEN to the door lock actuators. This means that if your passenger door lock switch is bad (or simply removed), then neither door lock actuator will function. When testing the circuit, remember that the actuator power for both doors comes from the passenger switch and the ground for both actuators comes off of the driver’s switch. The ground is located on the driver’s door and is shared with the power window switches. So, if your power windows work, you most likely do not have a ground problem. We have seen one instance where the actual door didn’t ground to the body when open (windows and locks worked fine with the door closed). For that repair, we ran an auxiliary ground wire from the ground screw on the driver’s door, through the door wiring harness, and attached the auxiliary ground wire to the chassis inside the left kick panel. Lastly, the ’86 and older Fox door lock circuits are the same, even down to the wiring colors, but they use a six terminal switch versus the five-terminal for the ’87-’93. However, don’t let that throw you, as the wiring still only uses five of the terminals. Just pay attention to the orientation of the switch in the wiring connector and you’ll see which terminal isn’t used.
Source
National Parts Depot
(800) 874-7595 FL Depot
(800) 368-6451 NC Depot
(800) 521-6104 MI Depot
(800) 235-3445 CA Depot
www.npdlink.com