Why Does My Car A/C Only Work When Driving?

I hate the heat and I’ve been noticing that my car’s air conditioning system stops working when I’m stopped at a red light or if I’m idling. Why is the A/C only working and blowing cold air while I drive?

Jason Tushinski · Answered on Jul 12, 2022
Reviewed by Shannon Martin, Licensed Insurance Agent.
This is a great question—if you live in a warm climate, your car’s air conditioning is vital to keep you comfortable. Odds are, your car’s air conditioning isn’t working due to one of the following: a malfunctioning A/C condenser fan, an A/C condenser blockage, a problem with your A/C compressor, or low coolant.
  • A/C condenser fan: Your car’s A/C condenser keeps your air conditioner cool. If this fan isn’t working, your A/C won’t be able to regulate the temperature inside your car. This is especially true when your car is stopped. The airflow from driving helps keep the fan working, so when your car stops, so do the fan and your A/C.
  • A/C condenser blockage: If your condenser has a blockage, you’ll need to clean it out. As well, when your car is stopped, no air is flowing through any unblocked parts of your condenser—so no cool air is passing through the cabin.
  • A/C compressor: The compressor is the central component of your car’s A/C system. The coils cool down the air going into the cabin. If the compressor isn’t cold, your engine needs to work harder to keep those coils cool. When your car is stopped, your engine isn’t working—so the coils aren’t being cooled, and neither is the cabin.
  • Low coolant: Coolant helps regulate your car’s temperature and keeps the engine at the desired temperature for proper function. Your car’s air conditioning needs coolant to work—and if it’s low or has run out, your car won’t cool down.
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