"rrs" wrote in message:  "The air conditioner is blowing warm air.  It was
proffesionally serviced last year and worked fine.  It hasn't worked at all
this summer.  I thought it had a leak so I added Freon.  The freon level
appears to be fine.  The condensor is cycling at approximately 5 seconds on
and off.  Could it be a bad thermostat or pressure switch?
If so, are they difficult to replace?  Any other suggestions?"

Do you mean the compressor is cycling on and off?  It could still be low on
refrigerant.  You need to put gauges on the low side to see what the
pressure readings are.  This will tell you if you are low on refrigerant.
Other possibilities is high pressure switch, bad connection at the plug on
the compressor, bad switch at the controls in the dash, bad WOT cutoff
switch (cuts the compressor off while in the passing mode) and many more
possibilities.

Sarge