Monday, September 30, 2013
When I Turn on the Air Conditioner the Fan Blows But the Outside Compressor Doesnt Come On
Since its introduction to the automotive world in the 1940 Packard, air-conditioning systems have been through many changes. The most drastic change was the shift from R12 to R134a, due to environmental concerns. When you turn on the air conditioner by pressing the power button and turning on the fan, you expect to hear the compressor kick on. There are six main reasons for the compressor not to turn on when you expect it to.
Incorrect Charge Level
All air-conditioning systems use a refrigerant to cool the cabin of the vehicle -- either R134a or R12. All post-1996 vehicles use R134a and prior to that, most vehicles used R12 refrigerant, commonly called Freon. The air-conditioning system requires a specific amount for refrigerant to run without causing damage. If the charge is low, most cars cut off power to the compressor to keep it from turning on.
Failed Pressure Sensor
Air-conditioning systems are under high pressure -- some exceed 200 psi. If the system has too much or too little pressure, damage may occur. Most modern vehicles use an air-conditioning pressure switch to monitor the pressures and cut power to the compressor if the pressures are incorrect. If this switch fails, no power can get to the compressor and it will not turn on.
Failed Wiring
The air-conditioning systems in all cars have a series of power and ground wires. If one of these wires fails, the compressor cannot receive power and will not turn on. This failed wiring can also cause additional problems with your vehicle.
Failed Air Conditioning Switch
To engage the air conditioner, you must press a switch inside the vehicle. If the electronics inside this button fails, the compressor will not turn on, as it will not receive power.
Blown Fuse
As with all electric systems in vehicles, there is a fuse that protects the compressor from power overload, typically 10 to 30 amps. If the amperage exceeds the limits of the fuse, it will break the circuit and the compressor will no longer receive power.
Failed Compressor
The compressor has a clutch on the front that engages and disengages as you turn the air conditioning on and off. If this clutch fails, it causes the compressor to either lock up or spin freely. If the latter is true, the compressor cannot turn on, as the power is not transferring from the drive belt to the compressor. If the former is true, the pulley locks up with the compressor and you will hear a loud screeching sound from the belt spinning on the stuck pulley.
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