Troubleshooting a Toyota Corolla AC System

Written by ross glyn
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Troubleshooting a Toyota Corolla AC System
Troubleshoot the air conditioning system in your Toyota Corolla before problems become too extensive. (car heater vent image by robert mobley from

Arm yourself with a few facts before taking your Toyota Corolla into the shop for what could turn out to be an expensive repair. Run through a few basic troubleshooting steps to determine what the problem might be. Most issues are fairly simple to diagnose, whether they involve the valve control, a malfunctioning blower fan or a blown fuse.

Skill level:

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Things you need

  • Air conditioner pressure gauge

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  1. 1

    Check that the dials and switches on the air conditioning panel are not damaged in any way. Ensure that both the electric blower fan and the air conditioner are turned on. If the fan does not kick on, a fuse may have blown, or the fan may be malfunctioning and need to be replaced.

  2. 2

    Check to see that there in coolant in the radiator. Refill as necessary. Inspect all the air conditioner hoses and components to ensure that they are free of damage and kinks. Have them replaced, if necessary.

  3. 3

    Attach the air conditioner pressure gauge test to verify the system has enough pressure. The gauge has a colour-coded hose. Connect the blue hose to the low-side service port, and the red hose to the high-side port. If the pressure reading is not between 22.7 Kilogram Per Square Inch (PSI) and 80 PSI, have a mechanic investigate this further because there may be a leak in the system.

  4. 4

    Start the engine and set the controls to the coldest setting. Check under the bonnet to see if the magnetic clutch attached to the air conditioner compressor turns over. If you do not see it kick on, the problem may lie with a fuse that has blown or with the wiring. It may also mean that the compressor has seized and may need to be replaced. Have a mechanic take care of this.

  5. 5

    Set the air conditioner's controls to the highest setting and start the engine. Place your hand just above the two hoses connected near the firewall. If both of the hoses are the same temperature (both hot), there may be a problem with the valve control One of the hoses should be slightly cooler than the other one. Have a mechanic check this out for you.

Tips and warnings

  • The compressor may not turn over if there is not enough refrigerant in the system. Have a mechanic refill the system with refrigerant.
  • If you notice a small amount of refrigerant leakage on some of the components, this is normal.

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