1. Look for: Oil stains on hoses and fittings. Evaporator outlet warm. System pressure low.
When leaks occur, lubricant and refrigerant will be lost which causes low pressure, as well as possible compressor damage due to the lubricant falling out if suspension. Always use new O-Rings and leak test entire system before and after service.
2. Look for: Frost around orifice tube or expansion valve. Evaporator outlet warm. high side pressure reads low. Low side pressure reads low to vacuum.
Compressor failure can send metal shavings and burned oil throughout the system. The receiver-drier or accumulator and orifice tube filter out these contaminates, and must be replaced to protect your compressor warranty. Evidence of flushing or installation of an in-line filter on accumulator system is also required.
3. Look for: There are no visible signs to indicate excess moisture.
The receiver-drier or accumulator contains desiccant which absorbs moisture, and should always be replaced with compressor, or with any service on a system five years old or older. Once the desiccant is saturated, moisture in the system combines with refrigerant to form acids, which will quickly destroy the system.
4. Look for: Poor cooling. high and low side pressures read high.
Too much lubricant in a system can bend or break valves and pistons. To correct, flush the system with approved solvent, drain compressor and refill with correct type and amount of lubricant.
5. Look for: Poor cooling at low speeds. Engine overheating. System low side pressure is normal to high. High side pressure is high.
It is essential that airflow be maintained across the condenser. An inoperative fan can be the result of a bad radiator fan motor, fan clutch, fan relay, fan control module or wiring.
6. Look for: Clutch that frequently cycles or does not cycle at all. Compressor may not operate.
Check for blow fuse or faulty wiring. Insufficient clutch voltage or improper air gap will cause premature clutch or compressor failure. Voltage at the clutch should be within 1.5 volts of the system voltage. With engine running the system voltage is 13.5 volts. Clutch coil ground circuits and control switches will also cause clutch and compressor failure.
7. Look for: Engine overheating. Poor cooling at low speeds. System high side pressure reads high.
Missing or broken fan shrouds, air dams or condenser sealing gaskets will divert air flow from the condenser and radiator. This will increase the condenser temperature and pressure which can result in compressor failure.
8. Look for: Engine overheating. Poor cooling at low speeds. Evaporator outlet cool to warm. System low side pressure normal to high. High side pressure reads high.
A vehicle with a restriction in the radiator or condenser will cause an engine to run hot and AC pressure to increase. Road debris, bent fins, bug screens and front end protection covers can also produce this condition.