Hi Guys,

I was hoping someone could help me out with a problem I have with the Air con in my 86 190e. My mechanic about a year ago decided to replace my klima relay with a standard four prong relay, since then i've killed my compressor once due to spinning it too quilckly i.e. 6000+ rpm and have constant problems with it freezing up, I finally got around to look at what the problem was and was shocked to find what he had done. Anyway back to the problem, I tried slotting back in two different Klima trying to find the correct one for my compressor (he used bullet terminals into socket for the other relay so this was easy) and it didnt' work so now i'm attempting to diagnose what other wiring he has changed.

On the Klima I have GK+, GK-, 87, 15, 31, T, KL, TD. Now this is what I have summised.

31,15 are go to the coil in the relay, obviusly intercepted by the electronics of the klima.

87 - compressor output

T - Evaporator Temperature signal

KL - Compressor speed signal

TD - Tacho signal

Now that leaves GK+ and GK-, I'm guessing that GK+ is +12 to power the compressor and circuitry in the Klima and GK- is gnd.

Can someone correct me if i'm wrong or make any comments that would help me figure out what he's done.

Sorry for the long post and thankyou for taking the time to read to this point.

Blair

GK+ & GK- are the compressor speed signal inputs. The circuit 15 is key on battery power. Circuit 31 is always ground.
KL is the command signal that comes from the pushbutton control that turns the compressor on. That is a GROUND signal!
T is the signal that the engine is overheating, that also is a ground signal form a switch in the waterpump. Ground on T will shut the compressor off.
87 is the power to turn the compressor ON.
87Z is a command signal to the fuel computer to raise the idle.

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Many Thanks MB DOC,

I couldn't figure out what he had done and couldn't get the Klima relay working so I actually ended up bypassing the Klima and wired the AC through my injection computer (Autronic). I programmed it to cut out the compressor if rpm reaches 4500rpm and if I throttle above 75%. Do you think 4500 is safe for the compressor, what rpm does the klima cut it out at? The only thing I dont have now is the belt slip cutout but I can't that being a problem.

Thanks again,

Blair

The Klima relay doesn't cut-out the compressor at speed. It uses the relative speed of the compressor and engine to see if the compressor is locked. It then uncouples the clutch to protect the belt and all other accessories (such as water pump).

As far as I know the compressor has no more trouble doing 6grand than does the motor.

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

I thought the Klima also cut out the compressor at speed, I know it used to on my car but that may have been the belt slipping.

Thanks for the reply,

Blair

I'm pretty sure it cuts-out the A/C compressor above 6500 RPM.

:-) neil

Additional Notes:
Connecting pin 87z to +12v signal will increase the idle to compensate the AC Compressor.

Thank you mbdoc,
Regards