C200 central locking problem

[bdross]

Hi all,

I was looking for some help with the following problem.

I have a 1994 C200 Elegance fitted with what I think is a Scorpion 918 alarm. The key fob normally enables/disables the alarm and centrally locks/unlocks the doors.
Recently the central locking started playing up. The fob arms and disarms the alarm but sometimes the central locking fails and the doors don't unlock. If I unlock the drivers door with the key I can get in but the engine won't start.
I can get around this by removing the fuse for the central locking, waiting a minute, putting it back. I can then operate the central locking with the key and the engine starts.
Had the local Mercedes Garage check it out and they said that the problem was the central locking pump. £400+ but they are in short supply and I might have to wait weeks.
Anyway I said that I could live without the central locking and could they disable the immobilizer so I could start the car when opening the doors with the key. They said the immobilizer was a function of the alarm and that the Scorpion alarm can be deactivated using a special key in a slot in the glove box. Took a while but I found the key.
So used the key in the glove box to disable the alarm.
Still have the same problem. With the alarm disabled and just using the key to lock and unlock the doors, if the central locking fails to unlock all the doors the car still won't start.
So I removed the fuse for the central locking, locked all the doors manually, came back later, opened the drivers door with the key and the engine wouldn't start. Had to put the fuse for the central locking back in and the engine started.

What I'm thinking is that the engine is immobilized by the central locking and not by the alarm. Could be the vacuum pump operates the starter immobilizer somehow.

Has anyone else had this problem? Or got any idea how the central locking operates the immobilizer.

Thanks in advance.

 

[Dec]

You have the same alarm as myself, do you have a red and green LED on rearview mirror? and drivers door? I don’t have a key lock on driver’s door, but I do have a lock on the passenger door so yours is a bit different to mine.

Do you have a flip out key with one button? If you do it is this button that controls the central locking AND the immobilizer, the Scorpion alarm fob, if you have one also controls the central locking but has nothing to do with the immobilizer so I would disagree with the following MB statement, at least in the case of my car.

“They said the immobilizer was a function of the alarm and that the Scorpion alarm can be deactivated using a special key in a slot in the glove box”

There is a comfort control module in the boot, right of battery (See link below) secured by 2 plastic screws, and the wires coming from it can get damp/wet if water is getting into boot. Inside a foam box is the central locking pump, located inside rear wing, right hand side of boot.

When you lock/unlock you should hear the pump running for a few? seconds.
Dose the central locking switch on the dashboard work?

http://www.boopolo.com/alarms/alarm.html
http://forums.mercedesclub.org.uk/attachment.php?attachmentid=4873&d=1206813076

Dec
Edit, replace that fuse with a new one and clean the contacts, just to eliminate it from your enquiiries.

 

[bdross]

Thanks for taking the time to respond.

I don't have the red/green LED on the rearview mirror. I have a single red LED on the dashboard.
Driver and passenger doors both have key locks.
The fob has 2 buttons and a slide as shown on the 918 user manual, only with the Mercedes logo on it.
Left button locks/unlocks, right button is panic. Slide toggles ultrasonic protection.
I've now disabled the alarm using the special key in the slot in the glove box so the buttons on the fob do nothing now.
The fault is very intermittent sometimes using the key in the drivers door will unlock all the doors other times it only unlocks the drivers door and the car won't start so I have to go through the routine of removing the fuse for the central locking.
The switch on the dashboard seems to work but I haven't done any serious testing using it.

It looks like the problem is with the central locking and not the Alarm. I'm not convinced the fault is with the pump as the pump does work, only intermitently.

I'll check out the comfort control module at the weekend as I'll need to remove the battery to get at it.

Thanks again for your help

 

[Dec]

I’m not going to be much use to you, we have the same alarm and year of car but a different wiring set up.
As far as I know the comfort control module controls the immobilizer and the immobilizer controls the pump, but maybe it is the other way around.

If it isn’t a faulty wire somewhere then it may be the pump or the comfort control module I was reading this a while back, it’s a different car and system but might be useful… http://www.mercedesshop.com/Wikka/W124Keyless

Its very odd that removing the fuse sometimes fixes the problem, perhaps when you disconnect the battery for a while and reconnect it, this might “reset” the comfort control module??? Your car is quit unusual in that it doesn’t have a flip ignition key or the two LED’s in the rearview mirror. Sorry I can’t be more helpful.
Let us know how you get on.

Dec

 

[bdross]

At the weekend, I removed the battery and comfort control module. Took a chance and opened the module, since it was easy to do, and cleaned all the contacts on the relays. Removed and reconnected all the wiring and sprayed with WD40. Put all back together and re-enabled the alarm. 4 days now and the alarm and central locking have been working without a problem. Might have been that disconnecting the battery has reset the comfort control module or maybe cleaning the contacts or the conectors has cured the problem.

Either way it's all working for now.

Thanks again for your help on this one.

 

[Dec]

Thanks for comeing back on that, hope it continues that way.

Dec

 

[clovis gregory]

clovis gregory

can any one tell me if its possible to test the central locking pump

 

[Dec]

You should hear the pump whine when you lock/unlock the car?
What car is it?
What year?
Can you describe the problem/symptoms?

Dec

 

[television]

Just an out line
These pumps have 2 means of cut off

If there is no vacuum leak the there is a bellow switch that cuts the pump within 2-3 sec,, if there is a leak then the pump will run for 18 sec and be electronically turned off.

As said you can here it run when its working