Door Lock Repair
Updated December 27, 2012
Every so often the door lock on the drivers side rear wouldn't open. I'd have to lock and unlock the doors a couple of times to get the door open. When it started getting to the point where I would have to pull the button up I decided it was time to fix it.
First roll the window all the way up. I pulled the door panel off by simply unscrewing all the phillips screws in the door. Lift the panel up and away from the door. You will have to unplug the power window switch. Then carefully peal the plastic moisture shield down so you will be able to re-stick it back on.
I cleaned up the whole area and door panel. The door button is connected to the lock mechanism with a cable. Make sure the cable is moving free. If it's not remove it from the door, flush it out with something like WD-40, lubricate it and reinstall.
All the rods and button cable come together at the door latch. Clean the mechanism by soaking it down with WD-40. Then re-lubricate it with oil or lubriplate grease. Make sure that the rods are moving free and not coming in contact with anything. Bent rods can cause problems.
Most problems turn out to be bad actuators. They don't have enough power to open and close the lock anymore. Most aftermarket units won't fit into the small area of the door. Aftermarket actuators cost about 4 or 5 dollars. You can use the AMG factory actuator (44.00) or an Omega DSQ-2SQ #330-582 (11.00).
Replacing an actuator is pretty easy. You undo the yellow clip that attaches the rod to the lock. Unscrew a small phillips in the door and reach around the window track and pull out the actuator. Unplug it and put a new one back in.
The moisture barrier wouldn't stick back on so I bought some 3m contact cement made for sticking sandpaper to a buffer at the paint shop. Just put a thin coating on the barrier and on the door; let them set for a few minutes until tacky, and put the barrier back on.
This is the inside of a lock actuator. It's just a small dc motor that drives a spiral shaft through small gear.
If one random door lock out of the 4 door locks won't work and the problem isn't the driver's door switch then you probably have an insufficient voltage to operate all 4 at locks at once. The most likely problems are a failing door relay, bad ground to the receiver or bad receiver. You will also find that an individual actuator or the connecting harness could be the culprit. In that case one door would not work with either the remote or the driver's switch. One bad actuator can bring down the entire system.
If one door consistently acts up, think actuator to the door or mechanical problem with the door lock itself. One of my doors would not work because the door button (really a cable) was frozen from rust and prevented the lock from locking or unlocking. If it takes alot of pressure to push down or pull up the button, think corrosion and mechanical failure. I replaced the cable. AMG part number for 1996 wagon: 5938896. I could easily lock or unlock the door manually once the cable was replaced.
If the actuators are OK then the problem may be the drivers master door switch. This problem could affect all or one door but will be consistent. Remove two screws and examine the connections or replace the switch.
Once the lock mechanisms were repaired and 1 actuator was replaced, I had rotating doors that would not unlock. All locked all the time using the transmitter or master switch. 3 of 4 unlocked when using the transmitter, and 3 of 4 unlocked when using the master switch (failed less often then the transmitter which always failed). Oddly, I could never predict which door would fail. Sometimes the driver's door, sometimes the rear passenger, it always changed. The one thing in
common was that the door that failed did not get a full 12 volts.
I had one heck of a time finding the location of the door relays. Ultimately, they were found under the center console on the doghouse.
I swapped the door open relay. Everything works all the time. I suspect the relay was loosing voltage and short changed one door circuit at random.
The door lock relay in my 1996 H-1 wagon is made by Bosch part number: 0-332-204-150.
Door lock Trouble Shooting Notes:
There are two black Bosch relays found under the drivers kickpanel at about
the level of the CTIS cluster (left of the steering column). Mine were
taped together with electrical tape. Another common problem is bad
connections at the level of entry into the door. Also, the master switch on
the drivers bezel can have a bad connection and cause a large voltage drop.
I have over the years had each one of these problems.
I would recommend using a multimeter and take readings along the electrical path to find your voltage loss.
Possible Door lock replacements:
Door Will Not Unlatch and Stuck Closed
by Keith Perry:
The driver's side rear passenger door will not open from either inside or outside the car.
First try to realign the door as it may have fallen too low over the years. Loosen the 4 hinge screws using a 1/4" 12 point socket and lift the door to a higher position. Tighten the screws. See if the door will now open. If not Remove the interior door trim (see above) which isn't easy with the door locked shut, but I managed it using a small right angled phillips ratchet.
Place a screw driver through an access hole in the door and hit it with a hammer. The door popped right open! Then realign the door as described above.