|Reiner’s Corner – Auto Repair Help
|DIAGNOSE – POWER DOOR LOCKS DON’T WORK PROPERLY
Continued from Part 1
POWER DOOR LOCK REPAIR TIPS & TRICKS
Apart from what has been stated in Part 1, diagnosing problems with power door locks is not always a straightforward affair, but one way to avoid confusion and misdiagnoses is to approach the problem logically. Thus, ask yourself the following questions in the order they are presented here, address one issue at a time, and base your actions on the repair options provided in this guide for each question. Also, be sure to check if the problem is resolved after each step both to ensure a successful repair, and to save time.Are all the door locks affected?
If none of the above steps resolves the issue, suspect either a defective door lock switch, or wiring issues. Proceed as follows-
Do the affected door locks fail to work consistently?
NOTE#1: Pay particular attention to the wiring in the boot between the doorframe and the door itself. Continual flexing of the wiring as the door is opened and closed can sometimes cause conductors within the plastic insulation to fail, with no sign of the failure being apparent during a casual visual inspection of the wiring.
NOTE#2: Be sure to include the affected actuator(s) itself/themselves in this step. Measure the resistance across the two terminals on the actuator(s), and replace it/them if there is no continuity, or if the measured resistance deviates from the value(s) stated in the manual by more than a few percent.
Does the manual switch now activate the affected actuator(s)?
If one or more power door locks fail intermittently, the cause is almost always bad electrical connections. Note though that some types of intermittent failures can be extremely challenging even for professional technicians to find and repair, so if an intermittent fault is suspected, repeat all resistance and continuity tests on all wiring (while vigorously wiggling) the wiring until the fault is found and repaired. Alternatively, refer the vehicle to a competent repair facility for professional diagnosis and repair.DIAGNOSING MECHANICAL PROBLEMS
Note that many problems with power door locks involve mechanical failure(s) of one or more components, with sticking and/or binding moving parts following close behind. One particular problem, that of locks cycling rapidly (especially on some Honda models) is described below-Locks that cycle rapidly
On some applications that are fitted with door locks that use DC motors, the control module depends on a voltage spike that occurs when the actuating lever reaches a built-in stop. In these cases, the actuating lever comes to rest against a rubber stop in the switch casing at the end of its travel, which causes a voltage spike that the control module interprets as a signal that the door lock had either locked or unlocked the door.
In many cases, the built-in stop either breaks off or wears away after long use, thus failing to produce the expected voltage spike. When the control module does not receive the expected voltage spike, it either interprets the lack of the signal as a failure of the system, or more commonly, to lock and unlock the door in rapid succession for as long as power is applied to the affected actuator.
Note that the only reliable, long-term remedy for this condition is to replace the actuator with an OEM replacement part to ensure proper operation of the door lock.Actuators that move slowly
This happens more often on actuators that use DC motors and gears than on actuators that use solenoids. On geared actuators, either moving/rotating parts wear out after long use causing them to bind or stick, or the lubrication inside them dries out, causing the entire unit to bind. Replacement of the door lock actuator is the only reliable remedy.
An example of a typical geared power door lock actuator is shown below. Note the presence of lubricant on the gears that can cause the unit to fail when it dries out, or to fail due to excessive mechanical wear on one or more parts.
Other mechanical issues include mechanical linkages that bind or stick, or door latches that stick or bind due to the build-up of dust and dirt inside the mechanism. Ideally, door latches should not be lubricated, but many mechanics spray all manner of lubricants onto (and into) door latches in efforts to “cure” some power door lock issues. Since few car doors are dustproof, dust and dirt eventually combine with excess lubricant to form a sort of “glue” that inhibits the free movement of parts in the door latch mechanism.
To check if the door latch mechanism is the problem, disconnect the mechanical linkages that connect the power door lock actuator to the door latch mechanism, and activate the door lock. If the actuator now moves freely, the door latch mechanism is sticky or binding. Replacement of the door latch mechanism is the only reliable long-term solution.
NOTE: In some cases, the power door lock actuator is incorporated into the door latch mechanism. On these applications, the entire assembly must be replaced with an OEM replacement part to ensure proper operation of the locking system.