Hi all,

I have an ML320 W163 2000.
I'm struggling to understand what the hell is going on at the moment.

When I bought the car, the front passenger FL (RHD car) door lock was starting to die and would only lock without manual intervention maybe 50% of the time. Conveniently a week later it died, I'd have to manually lock and unlock it with the key or by opening from the inside. This did affect the central locking system if the lock was up (unlocked) as the car would try to lock the doors in the following manner:

1. All locks down (except FL)
2. All locks up (all are now up, as the FL was already up)
3. All locks down (except FL)

The remedy was to either lock it manually, get out of the car and then use the remote to lock the car, or I could just press lock on the remote, all would lock just like the above sequence, and Id use the key to lock the FL manually.

Bear in mind at this point, if I had manually locked that door and then used the remote, I'd get 3 indicator flashes as per normal. If the door wasn't manually locked, obviously no flashes but after Id do it manually the car would be secure.

This was also a nuisance when driving, so my friends became accustomed to me yelling at them to lock their door before I drove off otherwise all the locks in the car would unlock, lock and unlock until someone manually pressed the FL door lock down.
I ignored this as it wasn't a security issue if I was attentive.

Last night things just got a lot worse.
I should mention right now this is not machine gun lock like I've seen in videos, it is nowhere near as fast. Mine lock and unlock at a frequency of 1 second. It also only tries 3 times (lock unlock lock if it was in the unlocked position to begin) The car also would not do this if I used the remote to unlock, it would unlock all doors except for the FL. It would also flash to indicate unlocked.

So last night in driving home, and the car is doing it again, this time sounds slightly different. I tell my friend to lock his door, and he says he has. But the car is still doing it. My first thought is 'another one has died' so I look for the door locks not moving when the car tries to lock itself. This is when it gets wierd:
The front door locks itself, and the RR unlocks. Then the RR locks and the front unlocks. The RL also seems to do the same. I can also hear the boot lock going off. Manually locking all locks except the drivers and then using the remote to lock doesn't remedy it, it locks the drivers door, and unlocks the two rear doors and the boot?

I have no idea what's wrong, which ones faulty as they're all now displaying weird symptoms, and I cannot lock my car. No matter if I unlock or lock, there is no indicator flashes.
If I press unlock once, the drivers door unlocks, then locks, but the RR door unlocks. I press unlock again, and the FR drivers door unlocks, and the RR locks.


What's wrong? How do I test the faulty unit? Obviously process of elimination is now out of the question.

Thanks

 

Unsure if related but only for the past few days, the car has made a single beep as soon as I turn over the ignition every time I turn the car on. Just one short beep, same sound as when the headlights are left on.

Also, upon closer observation, I've found both rear doors refuse to completely lock now, they try to pull down but won't go all the way down, and if I manually push them and then use the remote to lock, they shoot up.

The boot is also locking and unlocking uncontrollably but the switch actually moves completely and is capable of locking.

So confused !

 

First check and replace fuse #42 in the engine bay fuse/relay box.

Then replace the front left door lock (actuator) assembly. It's broken.

 

Thankyou very much! It worked! No idea how that made it do the above, but I'm not complaining

 

Fuse JUST blew again and now it's doing the same thing.

This time I heard the back hatch lock try to lock then unlock, and now the fuse is blown.

Something is overloading it

 

Maybe it's a short circuit in the front left door lock actuator. Replace it, then replace fuse #42.