door lock mechanism broken, but which one?

[Jinster]

I know I have a problem with one of my door lock mechanisms. But I can't figure out which one.

I have a MY97. No remote. No alarm.

When I try to lock from the driver side with 1 turn of the key:

• the driver side locks and unlocks
• the passenger side does nothing (stays unlocked)

When I try to lock from the driver side with 3 turns:

• the driver side locks
• the passenger side does nothing (stays unlocked)

When I try to lock from the passenger side with 1 turn:

• the passenger side locks
• the driver side locks and then unlocks

When I try to lock from the passenger side with 3 turns

• the passenger side locks
• the driver side locks

So which side is the fault? (when locking from driver's side, nothing happening to passenger side seems to suggest passenger side problem; but able to lock up the passenger side from the passenger side with the driver's side locking and unlocking seem to suggest driver side problem)

P.S: Both windows courtesy drop when doors are open, so the door-open sensing part is at least ok.

Edited November 9, 2010 by Jinster

[RFM]

The simplest thing you can do is to check error codes and the door lock functions with a diagnostic tool, based on the obtained results, you can than eleminate the existing problem. Otherwise it remains guessing, especially on cars without alarm and remote.

[Richard Hamilton]

When you lock from the passenger side you are physically turning the lock barrel, but when you lock from the driver's side the passenger side is locked by the lock motor. Therefore it would seem logical that the passenger side lock motor is at fault.

The reason that the the driver's side locks and unlocks (from single-locking with either side key) is that the system sees a fault (ie the passenger side is not locked) so immediately unlocks the car. Triple-locking tells the system to ignore the fault and lock it anyway.

[Jinster]

Thanks for both replies.

That's good deduction, Richard.

I didn't realise turning the key physically turns the lock to lock. I thought turning key sends a signal to activate the lock motor, which then locks the car.

If the action of turning the key replaces the lock motor actuating, then it sounds like my passenger side lock motor is the problem. My other symptom was after emergency locking the car from the passenger side, only unlocking the passenger side would unlock both doors; unlocking from the driver side only unlocks the driver door - against suggesting a passenger side motor problem. This all fits now!

I will crack it open and have a look at it this weekend.

Edited November 10, 2010 by Jinster

[Jinster]

Thanks for both replies.

That's good deduction, Richard.

I didn't realise turning the key physically turns the lock to lock. I thought turning key sends a signal to activate the lock motor, which then locks the car.

If the action of turning the key replaces the lock motor actuating, then it sounds like my passenger side lock motor is the problem. My other symptom was after emergency locking the car from the passenger side, only unlocking the passenger side would unlock both doors; unlocking from the driver side only unlocks the driver door - against suggesting a passenger side motor problem. This all fits now!

I will crack it open and have a look at it this weekend.

Rich, you were right. It was the passenger door.

Didn't even get to crack open the DLM and I already found the problem:

Two wire joiners and a few cable ties later, we were in business!

The problem was the wire holder holding the wires to the door frame came loose at some point, the wires got in the way of the window, and a dropping window sliced them in half. :)

Edited November 12, 2010 by Jinster