[W126 Coupe] Automatic Climate control.

[Dick Spellman]

Hi Carl,

Start with an inspection of  your monovalve as it may have a leaking 
diaphragm.  Best way to check is to pull the solenoid valve and 
plunger.   Look for gummed up screen and for any punctures or cracks in 
the rubber by distending it a bit.   All of the other likely problems 
were just detailed in the past week or two.

Regards,
Dick

On 8/22/2011 2:55 PM, Carl Hansen wrote:

> 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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