[W126 Coupe] Automatic Climate control.

[Carl Hansen]

Last time I drove my SEC in the hot weather I noticed that the a/c stopped working after a while. I did see the message that a couple of other members had the same problem so I figured I was in the clear. 
I checked the Aux. fan bridging the gap as described and it works. I pulled both relays one which is for high and the other for low speed Aux. fan. 
Both relays are working as I placed them alternately in the high speed fan socket but it seems that the low speed doesn't work. Is this because it is temp sensitive, I am guessing that the fan comes on slow at first then faster when required as the temperature reaches its peak? I let the engine run with the car half way out of the garage and a/c on full blast. Engine reaches full operating temp,a/c is cool at first, then goes on to blow warm 70f air and aux. fan never comes on. 
Finally I thought perhaps it could be the temp. sending unit on top of the thermostat housing. I connected the two prongs to my ohm meter while engine is hot of course, full contact. I replaced the plug, no fan, bridged the wires, fan comes on full blast. While I'm standing there wondering why the fan runs when I bridge the wires but not when I plug it in to the closed contact, suddenly the fan started up all by itself with the wire unplugged. Maybe I should go out and look for a pinched wire somewhere. That proved negative, no pinched wire. I checked it again this time with everything shut down. Turned ignition on pulled the sending unit plug and the fan came on, I'm baffled, any ideas out there.

Carl H 
1988 560SEC
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