How to repair a car door lock mechanism

Updated March 28, 2017

Stuck car-door locks can be a frustrating and baffling issue. Not being able to get into your car or having your automatic locking mechanism not work makes a difficult situation, but it is a situation that might be able to be repaired at home. Typically, broken car door locks have two main causes. The first is a gummed-up lock and the second, with the advent of electronics and automatic locking from a remote, is a short in a wire or the electric system.

Open the car door. Place the slender straw onto the end of the spray lubricant's nozzle. Many of the door-lock lubricants available at auto parts stores come with this straw.

Direct the straw into the lock's key hole and spray for three seconds. Wipe away any excess spray dripping down the door with the paper towels.

Test the door handle and lock by opening and closing the door multiple times and then by inserting and turning the key several times. If there is still stickiness apply another coat of lubricant to the lock.

Read the vehicle owner's manual and locate where the wiring to the automatic door locks are located under the bonnet of the car. Open the bonnet and prop open with the bonnet hitch. Attach one red lead wire clip to the red terminal on the battery. Attach one black lead wire clip to the black battery terminal. Attach the lead wires to the voltmeter and get a reading of the battery's charge.

Attach the other red lead wire clip to the automatic door lock red wire and the black lead wire clip to the automatic door lock black wire. Keep the voltmeter's attachments to the battery's lead lines intact. You have made a complete circuit between the voltmeter, the battery and the door wiring. Take a reading on the voltmeter. Compare this number to the battery only reading. If there is a volt difference of 2 or more volts the problem is in the wiring of the automatic door mechanism.

Remove the wires from the automatic door system from the battery. This fix lets you secure the vehicle with the door lock and key with no damage to the automatic system other than what exists.

Open the door with the broken lock. On the inside of the door look for four to five (vehicle depending) recessed holes along the edges of the door panel and upholstery. Use an Allen key to loosen the attachment allen bolts and remove the door panel from the inside. Find the door handle catch. Use the small Phillip's screwdriver to loosen and remove the attachment set screws.

Pry out the handle and lock, gently form the inside. Have an assistant gently push on the lock mechanism on the outside of the door while you pull on the inside. You will hear the black rubber gaskets on the door hinge move into the open position.

Slide the new lock into the door latch position where the old cylinder lock was just removed. Before you attach the set screws, align the new lock so it triggers the black gaskets on the door hinge. Do this by turning the key if the lock several times while moving the door handles. Listen and watch the door hinge to see the black rubber gaskets move.

Tighten the set screws on the lock. Put the door panel back on and turn the allen screws to the right to secure it back to the door. Do not over tighten as this may cause cracking on the door panel plastic.

Follow the voltmeter directions from step 2 to check the wiring with the new door lock in place.


Many vehicle warranties will be negated by changing out locks on your own. Check with your vehicle maker about your warranty prior to changing locks.

Things You'll Need

  • Spray-on dry lubricant with narrow straw
  • Paper towels
  • Small flathead screwdriver
  • Voltmeter
  • 2 sets red and black wire leads with clips
  • Vehicle owner's manual
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About the Author

A former Alaskan of 20 years, Eric Cedric now resides in California. He's published in "Outside" and "Backpacker" and has written a book on life in small-town Alaska, "North by Southeast." Cedric was a professional mountain guide and backcountry expedition leader for 18 years. He worked in Russia, Iceland, Greece, Turkey and Belize. Cedric attended Syracuse University and is a private pilot.