central locking!!!

[Voltman]

Hi everybody, 1st post here. When i use the remote to open the car in cold weather like today, the fuse on the central locking keeps blowing. I assumed its because a lock is frozen. If i use the metal key to open the drivers door everythings ok. Had the car into the stealership a few times to check it out but they could not find anything wrong and was advised that mercedes sell cars to a lot colder places than the UK and that cental locking systems should work in freezing conditions - they were very unhelpful. Anybody any ideas, its driving me nuts! The car is a W220 1999 S320. Thanks in advance.

[Hartzpartz]

As using the key still activates the lock/unlock servos, one would assume that these are not semi-seized and that the wiring to them is not damaged (shorting out).
There must be an output from the remote transceiver to the central locking relay/control unit so maybe it's a wiring problem in this area. Have you had anywork done prior to the fault occuring. New ICE/alarm maybe? Perhaps something has been damaged in the process?
Just had another thought (re:the cold weather bit!). Maybe it is a problem with one of the servos overloading. Does using the key maually unlock the drivers door? (i.e all the other servos work electrically apart from the drivers door which is opened by a rod when the key is turned).
The extra electrical load of this extra servo operating in cold weather may be enough to blow the fuse? Do all the doors & boot lock/unlock at the same speed?
I would probably start by lubricating all the servo actuators although this would involve removing the door cards. Bit of a pain really!

[Voltman]

Thanks for the reply.

Have you had anywork done prior to the fault occuring= No work has been done on the car since april last year when the drivers massage seat stopped working. The garage said the air line to the seat had come loose and replaced it.

Does using the key maually unlock the drivers door?= Yes and the fuse does not blow, only opens drivers door, not any others.

Do all the doors & boot lock/unlock at the same speed?= Yes, all locks seem to lock-unlock at same time except the boot when lock/unlock a motor can be heard running for approx 5 secs after.

I would also appreciate any advise you have on how to lubricate the servo actuators - ie the best way & which bits to remove to get at them.

I have now also had to disable the automatic door lock control as this also blows the fuse in cold weather.

Thanks in advance for any advise.

[Hartzpartz]

There must be a short in the wiring to one of the servos. To save a load of time and hassle, I would get a recommendation for a local auto electrician who should find the fault with minor disruption! Not all dealerships have fully trained auto electicians so you may have more luck with one of the mobile guys?

[Voltman]

Thanks, there's a local auto electrician around the corner, will give him a go. Would a short cause the problem only during cold weather though.

[Hartzpartz]

Is a bit odd I must confess, but the cold can do funny things to electrics (especially batteries!). When you say cold, are we talking 0 degrees freezing? If so, perhaps a servo is physically freezing causing the overload?
Just another silly thought, is the rating of the fuse you're replacing definately correct? (as per the owners manual).

[Voltman]

Have just spoke to somebody in mb tech dept about the above problem. They say the problem is almost certainly a leak on the vacuum circuit which is allowing moist air in. When its freezing weather, this will cause the moisture to freeze and block the system and cause an electrical overload and stop the system from working. They suggest i take the car to a 'stealership' and get it checked out. Local dealer has said this is going to be very expensive due to the amount of time & labour involved with an initial examination fee of £500 +vat approx. Does anybody have any info or can point me in the right direction to have a go at doing this myself, any help greatly appreciated.

[Hartzpartz]

The vacuum unit on my 190 is under the rear seat cushion in a rubber/foam box. Very easy to get to and change.....................can't speak for your car I'm afraid, but I'm sure someone out there will know?