Full-throttle Switch Doesn't Stop A/C (W124)

[Jeremy5848]

Now that I have an LED tell-tale so I can see when the a/c compressor is on or off, I thought I'd test the Klima relay to see if it really turned off the a/c at full throttle. To my surprise, it didn't. I'm just starting to look for the cause and wondered if anyone else has ever looked into this little-known "feature" of the car. This is on my 1995 E300D (W124, OM606NA).

All diesel (and gasoline too?) 124 models have a microswitch in the throttle linkage, connected to pin 4 of the Klima relay, to turn off the a/c compressor when the "throttle" is floored. (This is NOT the kick-down switch.) The microswitch grounds Klima pin 4 at full throttle and the a/c compressor turns off. In my case, either the switch is misadjusted or broken, something is wrong or missing in the wiring, or something is wrong with the Klima relay. Testing will tell me which, and I'll report it here, but I wondered if anyone has already "invented this wheel?"

Jeremy

[tjts1]

When I installed the 5spd I wired mine to turn off the AC when the clutch pedal is pressed in. With the AC on revs drop much faster between shifts so turning it off during the shift makes it consistent.

[Jeremy5848]

Tests complete as far as able today; the problem has to be in the switch, the adjustment of it, or the wiring from the switch to Klima.

1. Throttle-linkage-mounted microswitch DOES NOT switch at full throttle, at least not as measured at Klima pin 4 (VL terminal).
2. If pin 4 is manually grounded, a/c compressor switches off, so Klima and compressor are working correctly.

Looks like I need to pull the intake manifold and attack the switch directly.

[Jeremy5848]

Originally Posted by tjts1

When I installed the 5spd I wired mine to turn off the AC when the clutch pedal is pressed in. With the AC on revs drop much faster between shifts so turning it off during the shift makes it consistent.

Great idea!