A/C System Troubleshooting

1. Refrigerant systems must have an adequate, but not excessive charge.
2. Determination must be made whether the refrigerant system is governed by a cycling clutch compressor or by valves which control evaporator pressure.
3. The air distribution system (blower motor, switches, vacuum lines and air ducts) must be operational before checking the refrigerant system.
Check the blower; if inoperative, examine switches, fuses, connections, wiring and the blower motor. If blower is operating but the air output is low, check for loose wire connections or shorts, undercharged battery, dirty or loose switch contacts, or a faulty blower motor. Inspect the air distribution system for obstructions and ensure proper door operation.
If the blower is circulating the air but there is no cooling, check the compressor drive belt; ensure it is not broken or slipping. If the pulley is turning but the compressor shaft is not, check the magnetic clutch. On models equipped with a cycling clutch, the following hand check method will determine whether the problem lies in the refrigerant system or further testing of the distribution system is required.
1. With engine warmed up and at a normal idle, set selector lever to Norm, temperature lever to Cold and blower on Hi.
2. Place one hand on the evaporator inlet pipe and the other on the accumulator surface with the compressor engaged.
3. If both surfaces are the same temperature and colder than ambient temperature, refrigerant system is normal.
4. If the inlet pipe is cooler than the accumulator surface, refrigerant system is low on charge. Add small amounts of refrigerant until both feel the same temperature. Then add 14 ounces ( one can) of additional refrigerant.
5. If inlet pipe is frosted over and accumulator surface is warmer, proceed as in step 4.
The individual components of the refrigerant system will often give clear signs of their malfunctioning.