Volvo: 1993 Volvo 240 A/C Problem, 1993 volvo 240, volvo dealership

Question
Dear Ray,

I am having an air conditioning problem with my 1993 Volvo 240.  It will blow ice cold air in the mornings and evenings when the outside temperature is cooler, but when the outside temperature gets hot, it starts blowing hot air.  I do not think it is the compressor.  The pressure readings are good.  I called a Volvo dealership and was told it could be something called an evaporator temperature sensor.  However, I cannot find a part that is called that at any website I've found.  Can you tell me what you think this part is?  Also, what do you think could be causing this problem?  Sometimes, even if the temperature outside is hot, the AC will blow cold air for a few minutes and then start blowing hot.  I've even had it start blowing cold again even in hot temperatures.  My husband is a good mechanic, but is somewhat baffled by this.  Any help would be appreciated!  Thanks!

Answer
Sandy,
On the evap there is only a part called the expansion valve. That will ususlly cause the low pressure readings to drop real low almost into a vacuum. You test that with gauges on it while the A/C is not cooling. If the pressure is not to low (below 20 psi) then evacuate and recharge with the proper amount of freon. Often systems will operate like you have stated when they are a bit low on freon.