Hey guys, I have a 1994 Mercedes S320, I went to a car alarm store so that I could have a keyless entry system installed. there ,I was told to go fix the central locking system first. When the key is putto the door, it should lock or unlock all the doors at the same time. My S320physicalkey locks or unlocks only the door where the key is put in. If it's a fuse I can replace that but if it's the pump how do I reach it? I need a step by step guide on how to get to that pump.
Can anyone help please?
Thanks.

 

You need to trouble shoot, the pump is under the rear pass. seat in a foam enclosure. It produces pressure to unlock, vacuum to unlock. All the locks (trunk gas)are controlled by it, and it produces pressure for the lumbars, backup rods,supplemental vacuum for HVAC,and head rest release. It might be a fuse, but typically the motor is fried.

 

Keyless entry was a standard feature, at least in US models since the intro in 92, if you get the system working MB should be able to get you switchblade remotes $150 or so, forget, Ebay

 

Peter is correct. The PSE pump on these years/models is under the right/rear seat. No too difficult to access. Consider www.alldata.comDIY subscription for replacement guides. Pump assemblies are pricey - $300-500 on internet/E-Bay buys. Much more at dealer. Exact fit part number usually hard to find as a generic version introduced in later 1990s+ years that fits several models and adapters to fit to the hoses required. The pump can be rebuilt if you send off to a repair shop. Google searches work on finding repair/replacement PSE pumps. I went through two used pumps bought and finally had to combine parts into a workable pump. I need to consider finding a rebuilt pump for my W140 and send one of the versions I have in as a core. This pump performs several duties (door locking, lumbar+, alarm, window memory, other). he other vacuum pump in trunk does door/trunk closing assist). Later year models put both pumps in the rear then combined functions.

 

Thank you all. I removed the back seat and I found the PSE pump. There are some cables connected to it but I didn't know what to do. I do have a subscription from alldatadiy.com, their website helped me replace my blower motor ten days ago and the air conditioning is working great now, but I don't know anything about this pump. If the motor is fried as Peter said where can I get a good pump? I would love to replaceit myself if possible like I did with the blower.
Any idea?
Thank you all so much.

 

Good that you have alldatadiy.com . I found it easy to replace my PSE pump under pass rear seat, if I removed it first, found the exact part number, then looked on ebay or internet elsewhere for an exact fit. I ordered and the replacement ans installwas simple. Just be careful on the electrical connector as it is can be challenging to get off/on right. If the exact fit part number, the vacuum lines block will fit perfectly. If using a replacement but different part number PSE pump, the vacuum lines will need to be modified. If you send me your OEMpart number, I will check it for you.