Is your power door lock actuator bad?
There are several ways to find out if you have a bad power door lock actuator. First, find out if the door lock actuator works in any mode, i.e. does it work with the door switches but not the remote key fob? If the door lock actuator doesn’t work with any method, then the problem can be the door lock actuator itself, the wiring or the control module.
Symptoms of a failing door lock actuator
Door lock actuators are made in two styles: solenoid and DC motor. Each door has its own actuator. They can fail completely, where they don’t lock or unlock the door but don’t make any noise, or they can fail partially. In a partial failure, you’ll hear some noise coming from the door panel and the manual door lock button may appear to move slightly, but not enough to completely lock or unlock the door. That may lead you to think the door lock actuator linkage is binding. It’s not. That’s a dead ringer sign of a bad door lock actuator. The fact that it’s moving and making noise proves that the lock switch, wiring harnesses and actuator connector are good. It’s the lock actuator that’s bad. Replace it.
Normal versus abnormal door lock actuator sounds
A solenoid style actuator makes a single clunk sound when locking and unlocking. But a DC powered motor makes a much different sound because these units have gears. In normal operation you’ll hear a short whirring sound. However, as these units fail, the noise gets louder, indicating they’re worn and about to fail. Any grinding sound during the lock/unlock operation is also an indication that the actuator is failing.
Door lock actuators can also behave erratically
Some lock motor style actuators are designed with a rubber bumper stop component. The bumper stops the lever at the end of travel and cushions the movement to prevent gear breakage. The door lock controllers in these vehicles look for current spike once the lever reaches the end of its travel. If the rubber bumper breaks or fails in any way, the controller won’t be able to tell when the lock has finished its travel. In some cases the controller interprets the lack of current spike as a sign of a problem, causing the door lock actuator to lock and then immediately unlock. The actuator/controller can do this consistently or erratically. If you notice the door locks behaving erratically, don’t automatically assume you’ve got a bad controller. It’s most likely a failing door lock actuator. Unfortunately, it can be caused by any of the vehicle’s actuators. Worse yet, since all door lock actuators operate at the same time, they also wear equally. So you can replace the suspect actuator only to discover that the others require replacement as well.
Erratic operation can also be caused by a frayed wiring harness in the door hinge area or inside the actuator itself.
Another symptom of a potential problem with the power door lock actuators are door locks that behave erratically. If the actuators have any sort of internal or wiring issue, it may cause them to rapidly lock and unlock unexpectedly, or cause them to function intermittently.
How to start diagnosing a door lock actuator
Depending on the year, make and model of your vehicle, the power door locks are either free-standing, controlled by a door lock controller or controlled by a body control module. If your vehicle is equipped with an individual door lock controller of body control module, those units usually fail to lock/unlock all the door lock actuators, not just one. If only one door lock actuator isn’t working, chances are it’s not the control module (there are exceptions however). If you’re having problems with inconsistent door lock operation and your actuators are controlled by a module, start by pulling the fuse for that module and then re-installing it a few minutes later. This can correct a software glitch that’s common in late 1990’s to mid 2000 vehicles (especially Chrysler products). If your power door locks start working normally after a fuse reset, you have two options: you can yank the fuse and do a reset when the door lock misbehave again, or you can take it to a shop and have the door lock software updated to correct the problem.
Next, check the door lock switch and door lock actuator
You’ll need a computer safe test light or digital multimeter to perform these next tests and you’ll have to remove the door lock switch from the door panel and even the door panel itself. Refer to a shop manual for direction on how to remove the door panel.
Door lock systems operate the actuator by toggling positive/negative voltage to the actuator. Unplug the door lock actuator electrical connector. Then use your test light or digital meter to check for power and ground at the connector when you operate the lock/unlock switch. You should see the voltage polarity toggle with each switch activation. If you see that, it proves the switch and wiring to the actuator are good and the door lock actuator must be replaced. If you don’t see the voltage toggle, work backwards to the switch to isolate the problem.
How to replace a failed door lock actuator
The actual procedure depends on the year, make and model of your vehicle. Late model vehicles have the actuator built into the door latch assembly, forcing you to replace the entire latch. Older vehicles usually have a separate actuator. The actuator can be located away from the latch and operate the latch via linkage, or it can be attached to the latch by plastic clips or screws. To see and operate the latches/screws you’ll need a mirror and curved picks.
Which lock actuator should you buy?
Lock actuators are failing more often and that increased failure rate has created a business opportunity for aftermarket suppliers to sell replacements at a fraction of the price of the dealer. Many of these units come with a lifetime warranty despite the fact that they’re often poor quality units. If you don’t like replacing the factory door lock actuator, I can assure you that you won’t like it the second or third time around when the aftermarket actuator fails. Before buying an aftermarket door lock actuator, check out the reviews. Also, check online OEM prices from sites like parts.com.
©, 2016 Rick Muscoplat
Posted on by Rick Muscoplat