Delayed A/C clutch signal
 

I noticed that my 300SD a/c compressor clutch does not instantly kick in after start-up, when turned on. Once I rev the engine to 2K, it kicks in and stays engaged. it does not appear to be slipping at all, as I have watched it engage while being under the hood. You can start it up with the a/c already commanded on at the auto temp control head, nd it will not engage at all until the engine speed is increased. Is there a built in strategy to the KLIMA to make this happen this way?

One of it's input parameters must be at the edge of the envelope below 2000 rpm.

If they are all in spec, there is no delay in clutch engagement.

On the '86, I can hear and feel the engagement instantly upon pressing the middle button.

Is this one of those adjustable things? or Do I need to start hunting. It seems that this is a new thing that developed recently, as I do not remember it occurring a few months ago. The KLIMA looks new.

There is no adjustment. One of the input parameters to the Klima is probably at the edge of the range, as mentioned above. You'll need to find that input and correct it.

Those Germans think of most everything. I am wondering if RPM parameter may be at low end of the threshold.

Klima is supposed to watch the tachometer signal and not allow the compressor's clutch to engage until 10 seconds after the engine speed has come up to 600 RPM after starting the engine. This is according to the factory 1985 "Introduction into service" manual (page 170). If the tach signal and/or the timer circuit in Klima have changed over the years as the electronic components age, the delay could be more or less than ten seconds after who knows what RPM.

Jeremy