89 420SEL A/C control problem
 

Need some diagnostic help re: my intermittent A/C problem. It runs COLD one time, then next startup -- no COLDA/C, etc etc. (Note: there never has been a BLOWER problem per se -- of any kind.)

Today the air (1) came on cold in the AM; I turned off the A/C when parking.

(2) The next startup a few hours later, no cold air -- just the blower putting out warm ambient air in effect, but the COMPRESSOR WAS ON -- just did not produce cold air in the car (again blower producing warm air - not heater level hot air at all.) Turned off the A/C when parking again.

(3) The next startup, one hour later --- the compressor came on and the cold air developed normally ..... no problems of any kind.

It appears that some control flap or sensor or valve is operating erratically, even tho' the compressor/blower systems are operating.

Can anyone ID the probable cause for this kind of erratic action, where the
compressor comes on and produces COLD one time; compressor comes on and the blower system just pushes warm air in the car the next time???

Sounds similar to many other post this week - the switchover valve for the flap?

does anyone have a manual that shows a blown up picture of the AC stuff under the dash? these questions get posted all the time, but always have different answers. personally, my AC works great, but I only get heat when the engine has full vaccuum, as soon as the vaccuum drops, no more heat. is there a temp door flap, or vaccuum acuator, etc? if we had a diagram we could all reference, it would surely help.