* Evaporator Fan Motor: This motor blows air over the evaporator coil, which is where the cold refrigerant is. If the fan motor is failing, it might make noise (whining, clicking, grinding) before completely failing. No airflow means no cold air.
* Evaporator Coil Issues: The evaporator coil itself could be clogged with debris, restricting airflow. This could cause noise from restricted airflow or from the fan motor straining.
* Condenser Issues: While less likely given the recent compressor work, the condenser (located in front of the radiator) could be partially clogged with debris, restricting refrigerant flow. This could lead to overheating and a noisy compressor before shutting down.
* Refrigerant Leak (New Leak): Despite the recent recharge, a new leak could have developed somewhere in the system. This is plausible given the age of the vehicle. A slow leak might initially function, then fail.
* Pressure Switch: A faulty pressure switch could be cutting the compressor off prematurely if it senses low pressure (even if the system has sufficient refrigerant). This is a safety measure to protect the compressor.
* Electrical Issues: There could be a problem with the wiring, relays, or other electrical components associated with the AC system. An intermittent electrical fault could cause noise and failure.
* Compressor Clutch: Though the compressor is new, the clutch that engages it could be faulty. A noisy clutch could indicate slipping or impending failure.
* Blower Motor Resistor: This component controls the blower fan speed. If it's faulty, the fan might be running intermittently or not at all.
Troubleshooting Steps:
1. Listen Carefully to the Noise: Pinpoint the location of the noise. This can help determine the likely culprit.
2. Check Blower Fan Operation: Make sure the blower fan is running at all speeds. If it only runs on high, the resistor might be faulty. If it doesn't run at all, check the fuse and relay for the fan.
3. Check for Leaks: A mechanic with AC diagnostic equipment can check for refrigerant leaks using a dye test or electronic leak detector.
4. Check the System's Pressure: Again, a mechanic with the correct gauges can check high and low side pressures to see if the system is properly charged and functioning. Low pressure could indicate a leak, while high pressure could point to a blockage.
5. Inspect the Evaporator and Condenser: Visually inspect both components for debris or damage. It's usually easier to check the condenser visually, while the evaporator requires more disassembly.
Given the recent work, returning to the shop that performed the AC compressor replacement and recharge is your best option. They should be able to diagnose the problem efficiently, as they already have some background information on the system. Simply mentioning the new noise and lack of cold air should lead them to the root cause.
