Central locking malfunctions when freezing
 

Hi everyone,

The vacuum actuated door locks of my wife's (yes, I needed to state that) 1998 A Class won't work when temperature is below the freezing point. According to MB's service bulletins this is due to a leaking vacuum component and the fix is to find the leak, fix it, blow each line free of moist and then reassemble it all. That sounds as a LOT of work. However, when the fault occurs, the vacuum pump makes a lot of noise, resembling a small air compressor, and this makes me hesitate to do the prescribed fix - if the vacuum lines are clogged by ice, why would the pump be noisy? Considering its purpose is to make vacuum, a clogged line would only make the vacuum occur quicker, right? My hope is that the problem resides within the pump instead. Has anyone got a clue on what's going on here? I assume the central locking systems among different MB models are similar.

/Jan

Hi, just wondering whether you cured your problem with your central locking. I have exactly the same problem with my mercedes (1999 s320 w220). The fuse on the central locking keeps blowing as well (freezing weather only). I will keep you posted if i find a cure.

See the September 2004 Article "Central Locking - Electropneumatic security? Here's how it works and what to do when it doesn't." in Mercedes StarTuned magazine.

https://www.mbwholesaleparts.com/StarTuned

Thanks for the link, makes good reading. I'm going to try to solve the problem this weekend.