I am eliminating problems one by one to fix my AC on a w124 88 and I came across the kilma relay lately, I removed it to have a quick look and the merc mac told me it was the wrong one, it says "4 Zyl" he said it was for a 4 cylinder and mine is a 6, the female connector(on the car) was different to the male connector(on the kilma). Doesn't this seem wrong, it does to me, does anyone have some information on which kilma I should have and could this be the reason why the AC will not work? It does come on sometimes but then cuts out!

Had a/c problems a year ago ... clutch kicked off at same time as tachometer ... standard stuff.

Thought was Klima and confirmed by smacking it and getting a/c and tach function back so took apart and cleaned points and examined ... worked when I put it back in ... then stopped working again ... bought used one ... worked then stopped working .... removed and examined the overvoltage protection relay (OVP) ... opened it up and .... parts fell out! It was Tango Uniform ... repaired it by resoldering ... worked 4.0!

I had been warned that many believe Klima relay is at fault, but is usually the OVP.

Bought a new one anyway and replaced ... works 4.0 still.

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg

Interesting relationship that OVP can have. On diesels the lack of a OVP output turns off the EGR transducer which creats the engine speed signal for the tach and the Klima.

I can't think of any such relationship on a gas model. The OVP should not be involved with the car in question.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Its weird though becuase what my concern is that somehow I have the wrong Kilma in the car, I have taken it out and it has been tampered with as well. I have no idea on which is the exact one i should have. Where is the OVP becuase I am not familiar with this car, that might need replacing as well. If i have a faulty Kilma then the compressors speed sensor will not match engine speed and therefore cutting the compressor out right?

I looked up the klima for a 300E to see if it was also used by 4cyls. By the number it doesn't. The relay watches that the speed number ratio stays the same no matter the numbers. I don't know if it also has expectations.

If it expects a certain ratio between rpm of the compressor and the engine (which would change with engine cyls because the speed signal is actually just a punch of pulses divided by 4 or 6 sorta) then the system would always shut off after starting up. If it has ever worked with that relay then the amount of cylinders don't matter. It still might be bad, but whether the part is wrong is an either or situation not a maybe all of a sudden.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Ok thanks I will go to the dealer here and see what the replacement for this exact car would be, even the male and female connections are different so i really haven't a clue but thanks for your concern. Would you happen to know what gas needs to go into the aircon and what oils and/or other things for re-filling?