98 Blazer w/climate control- intermittent AC

The AC on my 98 Blazer with Electronic Climate Control only works some time. Often when I start the vehicle, the light on the AC switch no longer comes on and the compressor does not engage. If I push the AC switch the light flashes 3 times and goes out. If the light comes on when I start up; the AC works fine. I usually leave the controls set for auto control but I've tried all positions when the AC doesn't work to no avail. The heater and everything else works fine. The system is fully charged and works great when it does come on or if I jump the AC clutch relay. There is no voltage at the AC request pin (D8) on the AC control module, as checked at the high pressure switch, when it quits, but battery voltage when it works. Is it just a bad control module or is the PCM or something else telling the module not to turn on the AC? My code reader only reads PCM codes and nothing is set. Are the 3 flashes of the AC button any clue? I would appreciate any ideas. Thanks very much.

Yes they may be trying to tell you siomething.
You need to fins a body/ac control apable scanner and get codes.
Post back codes.
Have you tryed to recalibrate it?
Any dead battery or charging system problems?

I wish I had a scanner that can read body codes. I've never seen a consumer type scanner that could. Does anyone know of one? Can the local repair shop read body codes with a Snap On or similar scanner or do I need to go to the dealer? I'm thinking the problem might be the ambient air temp sensor. I suspect a bad sensor will keep the control module from engaging the compressor and causes the AC button light to flash when I push it. Any comments? Thanks very much.

Yes a good repair shop with a good snap on body capable scanner will do it.

And always make sure the r-134a is a full charge.
Low charge or pressure switches will shut down the controls.
Good Luck
and let us know how it goes.
MT