1999clkcab

Hello im Richard, just joined on here as ive got an issue with my roof/ rear headrests
whilst all the posts seem very similar to my problem and have been a big help I was wondering if anyone else has come across this.
Today when I started for some reason I pushed the headrest button, they then went up and carried on going up and wouldn't stop. the motor was running even when they reached the top. pressing the switch down had no effect
I tried to lower the roof but as the headrests were up it wouldn't go.
so in the end the only way to stop the motor was to pull the 40amp fuse in the boot.
I read on here about the reset which I tried and to my relief has cured the headrests and the roof will function correctly.
but the motor is still running in the boot with or without the ignition on.
again ive pulled the fuse..
reading your posts this sounds like the relay is sticking.
but as every other post the headrests had gone off through shock and no one has appeared to have had the wayward wandering headrests at stand still I thought id ask...

Top Hydraulics

Richard,

welcome to the forum, and thank you for your detailed description. If the hydraulic pump in the trunk (boot) area will keep running even with the ignition off, then you very likely have a sticking relay. The relay is located next to the pump. For access, study the relevant section of this DIY guide: http://www.tophydraulicsinc.com/W208...eplacement.pdf.

Once you have created access to the relay, you could try to confirm by swapping it with the fuel pump relay, but this is almost a sure thing. The relay is MB part number 0025421319, aka A 002 542 13 19. It is a 50A relay with a suppression resistor.

It is good that you have pulled the 40A fuse before the pump motor burned out. Sticking relays are the main reason for W208 CLK hydraulic pumps needing new electric motors, because the electric motors are made only to run a few minutes maximum at a time. By the way, the pumps are designed to run dry (without hydraulic fluid) for up to one minute.

The electric motors on these pumps pull a good amount of current upon start-up, and that is what usually will spot welds the contacts together on old relays. It does not matter whether you are moving the headrests or the top - the start-up current is the same. Some motors will go bad without a sticky relay, usually from running for too long and overheating. If the motor itself is compromised, then it will usually draw more current and in turn will be more likely to make the relay stick. (Just mentioning this for completeness.)

If your headrests had been ratcheting up slowly by themselves (not emergency deployment and not initiated by you activating the roll bar button), then you would have an issue with the roll bar valve, but that does not seem to be the case here. (See http://www.tophydraulicsinc.com/en/w...d-service.html.)

I will add a few words about pump rebuilds, while we're at it:
As you have read on the forum, replacement pumps cannot be purchased new any more. Even Mercedes-Benz will sell only refurbished pumps at a very high price, and with core exchange. Top Hydraulics charges $600 plus shipping for CLK pump rebuilds, which includes a new high-current relay, the electric motor gets replaced if needed, and electric components in the motor get upgraded. Internal seals get replaced, valve block, check valves, relief valve and solenoids get serviced (solenoids get replaced if necessary), and in final test we make sure that the pump exceeds OEM specs for pressure, flow, power under load, and thermal behavior under load. See http://www.tophydraulicsinc.com/en/w...ulic-pump.html

Relevant pump part numbers:
2088000030 aka A 208 800 00 30 (early model years)
2088001048 aka A 208 800 10 48
2088000230 aka A 208 800 02 30
2088001748 aka A 208 800 17 48 (all models starting with VIN -070018)


Klaus

www.tophydraulicsinc.com
http://www.tophydraulicsinc.com/en/23-w208-clk

Here is a location drawing for the most commonly failing hydraulic components in the CLK: