A.C. Problem..

[McDiesel]

1992 300 turbo diesel 2.5 5 cylinder...

the air conditioning yeseterday worked fine on the way to work..

when i went to lunch it worked fine ... 40* degrees on my thermometer in vent.. 95* outside..

on way back from lunch the ac would not engage...

on way home ac again was inoperable.. blower motor is fine.. I just replaced the orig one in spring of 04., no cold air.. freon level is where it should be

about 40 miles into my trip home i switched on the air and it WORKED GREAT AGAIN.. got home restatred and all was fine..

today i go out this am it worked fine drove 5 miles to get a hair cut..
came out HAD NO AIR COND ANAIN AND NOW ALL OF A SUDDEN THE TACHOMETER IS NOT WORKING..

any ideas?? LISTED BELOW THERE ARE SO MANY THINGS THAT CONTRIBUTE TO THE AC SYSTEM and of course its saturday the mechanic is off!!

mono valve ? to the touch after running it would fry an egg!
Coolant Temperature Sensor?
Coolant Temperature Sensor/Switch (For Computer)?
Cooling Fan Motor Relay?
Cooling Fan Resistor ?
Condenser Fan Resistor ?
expansion valve?
compressor clutch relay?
compressor control module?
Condenser Fan Motor Relay?
Evaporator Temperature Sensor/Switch?
Heater Core Temperature Sensor/Switch?
Pressure Sensor/Switch HVAC?
Cooling Fan Temperature Sensor/Switch?
Heater Control Valve?

Going to let the car sit all day and see if about 8pm tonight the damn air come on or not! then i suspect the Mono vale if it stops when car gets hot...

looks like im headed to the hvac woes!