Automotive Air Conditioning Information Forum (Archives)
what usually happens to head pressure when
Drake57 on 
Thu September 02, 2010 5:27 PM 
evaporator (vent) fan stops running? I've a car that the vent fan quit, compressor cycles off/on due to thermo switch (I think). Pressures seem normal (175 hi, 40 lo). Can vent fan failure cause overpressure?
Thanks, Drake.
iceman2555 on Thu September 02, 2010 7:49 PM 
It is assumed you are speaking about the blower fan on the evaporator. If so, no,not normally will this result in excessive head (discharge) pressures. What could occur is that the system could pump liquid refrigerant into the compressor...and that will result in serious problems. The cycling is the result of the low pressure or evap temp sensor shutting down the compressor because the evap temp/pressure is falling below a certain range due to the lack of air flow and the super cooling of the evaporator.
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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
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GM Tech on Thu September 02, 2010 8:46 PM
that is how I test cycling switches in hot weather- unplug the blower motor
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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
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