There's no reason to tolerate a car that's full of hot air.
To those born and raised in extremely temperate environments, air conditioning is often a luxury on par with the electric toothbrush and bidet. However, an A/C breakdown can spell disaster for those who aren't used to sweating for six months out of 12. Fortunately, A/C systems are fairly simple, and there aren't too many things that can cause one to blow hot air instead of cold. Does this Spark an idea?
A/C Basics
An air conditioner works by compressing a gas refrigerant and then releasing it. Gases get hotter when compressed and cool off when they expand; that's why the air coming out of an air compressor hose is always so cool and refreshing. An air conditioner compresses its refrigerant gas, causing it to heat up. That gas then passes through a radiator, which cools it down. The gas then enters a second radiator, where it expands and cools down. Cabin air passes through that second radiator, cooling down in the process.
Low Coolant
If your cooling system is low on refrigerant, the compressor won't be able to squeeze the gas down. No compression equals no heating, which means no expansion and, thus, no cooling. Your A/C system's high-pressure lines are like its fuel gauge; when the pressure drops, it's time to recharge it with refrigerant. If you're working on an automotive A/C system that doesn't have an integral gauge, you need only connect a pressure gauge to the pressure access port in the high-pressure line coming out of the compressor.
Internal Leakage
Compressors are like engines in that they rely on a series of valves, seals and rings to seal their pressure chambers and prevent pressure loss. A well-used A/C compressor has worn seals and rings, which may bleed pressure from the high-pressure side into the low-pressure side. The end result is that system pressure on the high and low sides equalize, and the system stops working. In some cases, the low-pressure side of your A/C system may read slightly higher than it should. This is a result of pressure equalization and may indicate bad compressor seals.
Compressor Not Engaging
A number of things can cause the compressor to disengage or fail to engage. These faults are generally electrical in nature; either the compressor isn't getting power, or the thermostat isn't functioning properly. However, in a home A/C system, a bad thermostat will shut the unit off completely instead of allowing it to blow hot air. Automotive applications generally use a magnetic clutch to lock the compressor input shaft to the drive pulley. These circuits have a fuse which, if blown, could indicate a seized compressor. If your A/C fuse blows every time you turn the system on, then odds are the compressor has seized, and you'll need a new one.
Tags: coming compressor, cools down, low-pressure side, passes through, seals rings, second radiator