CL 600 c215 central locking

[Tony Huntb]

Car will not unlock on the fob. Lights flash three times so immobiliser off. Car locks on the fob. Maybe a factor but probably not. Had a recent new battery as was flat after a lack of ouse over a two week period. Any ideas where to start on this? Due in for a load of work but not until 1st of Sept and Pentangle are flat out.

 

[Naraic]

Do you have 2 keys? If yes, does the same thing happen with both?

 

[Tony Huntb]

Do you have 2 keys? If yes, does the same thing happen with both?

Only the one key.

 

[Naraic]

Does it lock/unlock using the switch on the dash?

 

[Tony Huntb]

Does it lock/unlock using the switch on the dash?

Will lock but not unlock when I press that button.

 

[Naraic]

So, not the key. That's as far as I can go. Anybody else able to help?

 

[Craiglxviii]

Are any fault codes displayed? First port of call!

 

[bluesl]

CL600, same generation as my SL55. Central locking is done pneumatically using the PSE pump in the boot. This can generate pressure or vacuum to lock and unlock. It sounds like the PSE pump (which has a lot more going on, solenoid valves to select which airlines are activated and whether pressure or vacuum is required) has partially failed. Listen for the noise of the pump when you lock. Check also other functions like soft close of boot and doors. The pump is a nightmare, £1000 for the dealer to diagnose/replace.

 

[grahamcol]

I’m thinking PSE pump too. My mate had a CL500 with locking / unlocking problems and he had the PSE pump repaired. You’ll need to Google this but there’s someone in the U K doing the necessary repair, or at least there was a few years ago.

 

[bembo449]

wouldn't the PSE pump failing pop the fuse ??

 

[bluesl]

The fact the car can lock but not unlock suggests the pump can create pressure but not vacuum. It does that by swapping the inputs and outputs of the pump by switching solenoid valves. It’s a ludicrously complex system which I believe Mercedes have now abandoned.

 

[Craiglxviii]

I was going for PSE initially. Could be valve failure.

Tony, if you’re in the Home Counties try Welwyn Merx, they’re used to 215s and their many quirks.

 

[brandwooddixon]

If you want to check it, the pump is under the right hand rear passenger seat with the fuse for it being in the fuse box accessible in via the panel in the footwell for the same seat.
If its operating in one direction then the fuse is probably okay.
It may not be the pump, its possible that there may be a leak in the system that allows for operation of the lock in one direction and not the other (not unknown for the diaphragm in the lock actuator to split).