SL/R129: Central Locking/Ifrared
Thread Starter
Junior Member
Joined: Sep 2021
Posts: 59
Likes: 2
From: Ann Arbor Michigan
1996 sl 500
Central Locking/Ifrared
So, I have a 96 R129. Currently the locks will not unlock with the fob. They lock as they should.And they lock/unlock when using the key in the door. I have been checking wiring and have not found any continuity issues. I have pressure tested the tubes and there are no leaks.
When I press the fob to unlock, the mirror flashes correctly, but PSE pump does not come on. However, if I remove the tube from the pump, the PSE runs and provides pressure.
Any ideas?
When I press the fob to unlock, the mirror flashes correctly, but PSE pump does not come on. However, if I remove the tube from the pump, the PSE runs and provides pressure.
Any ideas?
Last edited by kwelch02; Aug 8, 2025 at 10:18 PM.
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,308
Likes: 62
From: Bethesda, MD
2000 SL500
I have a similar issue with my 2000 sl500. Lights flash when I lock or unlock using keyfob but nothing happens. When I use the lock/unlock button in center console everything tries to work. My passenger door was locking/unlocking as it should so I replaced my door latch lock and the actuator in the drivers side.
now nothing works at all. I used a mityvac hand pump and tested vacuum and pressure on every line by removing it from the pump. Everything held which tells me there is no leaks, so now I’m assuming it’s the pump that’s giving me issues.
as far as the keyfob only flashing the lights from my research it could either be the IR receiver at the door or the signal from the n54 unit (sometimes called all activity module, immobilizer, etc). I replaced the IR receiver at the door and no luck so I’m assuming I have to take that n54 apart to diagnose that. My next step if I decide to chase this down is to find a new used pump on eBay but it’s hard to find one of the newer pumps with mkl (I have the lumbar support seats)
also wondering if I buy a pump without the mkl option it will still work for me as I don’t use the lumbar support anyway…
now nothing works at all. I used a mityvac hand pump and tested vacuum and pressure on every line by removing it from the pump. Everything held which tells me there is no leaks, so now I’m assuming it’s the pump that’s giving me issues.
as far as the keyfob only flashing the lights from my research it could either be the IR receiver at the door or the signal from the n54 unit (sometimes called all activity module, immobilizer, etc). I replaced the IR receiver at the door and no luck so I’m assuming I have to take that n54 apart to diagnose that. My next step if I decide to chase this down is to find a new used pump on eBay but it’s hard to find one of the newer pumps with mkl (I have the lumbar support seats)
also wondering if I buy a pump without the mkl option it will still work for me as I don’t use the lumbar support anyway…
Junior Member
Joined: Nov 2008
Posts: 21
Likes: 2
From: Cali
1990 300sl, 2004 E320, 2015 G63 AMG
OEM Infra-red Keyfob Delete
I have a 1990 300SL, owned for over 20 years with 230k miles. My original infra-red key fob still works though sometimes slow to respond when pointing to door or trunk receiving sensor window. I had a stereo shop install an AutoPage alarm system. They connected it to the vacuum pump to auto lock the power locks when simultaneously arming the alarm, with radar sensor. This was done over 15 years ago and still operating to lock all doors, trunk eyeglass door and all else as originally designed by Mercedes, using the AutoPage keyfob. No need to aim the keyfob as in the OEM infra-red fob.
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