Toyota flashing AC light

Diagnose and fix Toyota flashing AC light

Toyota has devised a test to check for a slipping AC clutch. Since it knows the engine RPM and the AC compressor pulley diameter, it compares pulley rotation to engine RPM via a sensor in the AC compressor clutch. If there’s a mismatch, you get a Toyota flashing AC light.

Check serpentine belt tensioner

Your first step in diagnosing a flashing AC light should be to check AC compressor belt tension and belt condition. If the AC compressor belt in your vehicle is tensioned by an automatic belt tensioner, follow the testing steps in this post. If the automatic tensioner is worn, replace it.

Check serpentine belt for wear and slipping

Next, check the condition of the belt. NOTE: Newer belts are made from EPDM rubber. EPDM rubber does NOT crack like older neoprene belts. YOU CANNOT CHECK THE CONDITION OF AN EPDM BELT WITH A VISUAL INSPECTION. You must use a wear gauge. Measure the wear on an EPDM using this method. If the belt is worn, replace it.

Check the AC compressor clutch relay

Toyota has identified a problem with their AC compressor clutch relays. Over time the contacts in the relay become pitted and build up electrical resistance to the point where it reduces current flow to the AC compressor clutch coil. That reduces the magnetic field, which in turn causes the AC compressor clutch to slip.

Check the part number of your AC compressor clutch relay. If the part number on the side of the old relay is 90987-02022, replace it with an updated relay, part 90987-02028. Then operate the AC and see if the Toyota flashing AC light goes out.

If the updated relay doesn’t fix the problem and you’re sure the belt and tensioner are good, then the problem is with the AC compressor clutch.

©, 2019 Rick Muscoplat