Door won't lock/unlock using manual button or electric door lock motor

[mrman]

Hi folks,



I found a few threads to do with central locking but my problem had nothing to do with this problem so I started a new thread.
Car: 1988 Milano 2.5
Symptoms. Central locking in the car causes all doors except the rear drivers side to lock and unlock. The manual button in the door did not go up and down when all the other door buttons went up and down. Furthermore, manually pulling the button to the unlock or lock position would not cause the door to lock. NOTHING could make this door lock.


Investigation: I popped out the plastic cover covering the 2 philips head bolts holding the interior door handle to the door. then took out the 2 bolts (you need a big philips bit). Next, there were 3 or 4 plastic push pins that secure the bottom of the interior. You simply have to be careful and pull the trim to pop out one at a time. if you break them, Canadian tire or any autoparts store should have replacements cheap. Then I removed the manual lock/unlock button by taking a hex bit and sticking it down the top of the button (you need to remove a small cover at the top of the button to see the spot to stick the hex key). Then you slide the whole interior door fancy trim thing up (vertical) and it should pop away from the bottom of the window. Remove the insulation.

Fix: I had two problems which I have since resolved and hope to help others by posting this thread.
1) I noticed a small nut was loose which was the pivot point for the lever connected to the button. when I tightened it - I could manually lock/unlock the door with the button.
2) the door lock motor was not working. I disconnected the red and blue connector. This wire harness from the car applies 12 to one wire and common to another to lock the door, then reverses polarity to unlock the door. I checked the resistance of the motor and it was about 2-4 ohms (right where a motor should be) so I knew the windings were good. However, the thing that is supposed to move back and forthe when the motor activates was seized. This unit does not dissassemble (no screws, only a single plastic moulding). Since I had nothing to loose and I wanted to find out what is inside, I took a hacksaw and carefully cut along the line that you could tell was where they joined the 2 halves together at the factory before the 2 pieces were melted together. Be careful! I cut along the whole parameter and was able to separate the top. Make sure you pay attention to the 2 gears and how it all will go back together. Strip all the rears off until you see the shiny metal motor shaft. Then I got the actual electric motor out of the plastic housing. its shaft was seized solid. I couldn't turn it with pliers without thinking it might break off. I set the motor in a vice (gently) and pryed open the 2 small metal tabs that keep the plastic back held in the metal housing. Only pry out these metal tabs as much as you need to since you will need to bend them back when reassembling. then gently pry out the plastic backing. I could immediately see there was so much corrosion and dirt in there. I carefully cleaned the windings. you can use a toothbrush but be careful! also, I blew out the junk in the metal housing. then took fine sand paper and cleaned up the copper armature contacts just until the bare copper showed through and all the corrosion was gone. do not sand any more than you need to. Then I put the armature (winding part) back in the housing. remember to put the small shiny thin washer on the top of the armature before inserting back into the housing. Next (gee this is a long thread sorry)... gently place the plastic backing on the armature and put gentle pressure on it pushing it towards the metal housing. BE CAREFUL not to bend the brushes. to move them out of the way there are 2 small holes in the plastic back. you can insert a small screw driver and gently pry the brushes out of the way of the armature and then the plastic backing will slide right into the metal housing. make sure the motor shaft spins freely. check the resistance again - is should be in the 2-4ohm range. be very careful and apply 12V and gnd to the connector contacts. the motor should spin. Then reverse the polarity - it should spin the other way. If all is good then bend the small metal housing tabs back in to hold the plastic back in place. only bend them as much as you need to to hold it... this isn't an engine block... next reassemble everything. i put a tiny dab of grease on the gears. Put the plastic top half over the bottom half containing the motor and gears. make sure the shafts line up. tie wrap the 2 halves together in 2 places or more (i did it in 3 places to be sure). re install and test. all is cool in my car. now that I think about it... The problem occurred due to moisture getting into the motor. I probably should have run a bead of silicon around the 2 halves... but the car lives in doors and never sees rain so it shouldn't be a problem.

hopefully this long thread will help someone do in 1 hour what it took me 4 to figure out.