Question: The car made intermittent whining noises in the engine compartment for several days. Then the air conditioner stopped working. It’s blowing hot air. I do not hear or feel the compressor engaging. Has the compressor most likely failed or is it another problem?

Based on your description, it’s possible that the issue is with the air conditioner compressor, but it could also be due to other components in the air conditioning system.

Here are a few possibilities:

1. Failed Compressor: The compressor is the heart of your vehicle’s air conditioning system. If it has failed or is not engaging, it cannot circulate refrigerant and cool the air. The whining noise could have been a sign of compressor bearing failure.
2. Low Refrigerant Levels: If the refrigerant levels in your vehicle are too low, the AC system cannot cool the air effectively. A low refrigerant level could also cause the compressor not to engage to avoid damage. Leaks in the system are a common reason for low refrigerant.
3. AC Clutch Failure: The clutch on the compressor is what allows the pulley to engage and disengage from engine power. If the clutch is not working, the compressor cannot do its job.
4. Broken Condenser: The condenser’s job is to cool the refrigerant. If it’s damaged, the system might not cool the air effectively.
5. Faulty Cooling Fans: If the fans that help cool the refrigerant in the condenser are not working correctly, the system might be unable to cool the air effectively.
6. Electrical issues: A problem with the wiring, a blown fuse, or a malfunctioning switch could also cause the AC to blow hot air.

To properly diagnose the issue, you would need to have a mechanic perform a series of tests, such as pressure checks, leak detection, electrical system checks, and possibly others. They can then help you determine the exact cause and the necessary steps to repair it.

Question: A car has AC that only blows cold when the car is moving forward. It does not blow cold when stopped with the engine running. Is this a compressor problem, fan, or something else?

If your car’s air conditioning system only cools when the car is moving, it might suggest an issue related to airflow or the cooling system itself. Here are some possibilities:

1. Radiator or Condenser Fans: If the fans are not working properly, they may not be able to provide enough airflow through the condenser to cool down the refrigerant, especially when the car is stopped. When the car is moving, the natural airflow might be enough to compensate.
2. Refrigerant Charge: Low refrigerant can also cause this problem. If there isn’t enough refrigerant in the system, it might be able to produce some cooling when helped by the higher pressures generated at higher engine RPMs or when moving, but not enough to cool when idling.
3. Compressor: If the compressor is weak or failing, it might not be able to compress the refrigerant enough at lower engine speeds to provide cooling. When the car is moving and engine RPMs are higher, it might be able to do a sufficient job.
4. Engine Cooling System: If the engine’s cooling system isn’t working properly (like a failing water pump or clogged radiator), the excess heat could be transferred to the AC system, causing poor performance at idle.
5. Blend Door Issues: This could also be an HVAC system issue where the blend door (which controls the mix of heated and cooled air) isn’t functioning correctly.

These are just a few potential causes. A professional mechanic should be able to diagnose and fix the problem accurately.