Toyota AC light flashing — What it means

Why is your Toyota AC light flashing? Here’s the scoop

If you have a Toyota AC light flashing condition, the problem may not be as bad as you think. Toyota AC compressor clutches use a lock sensor circuit to make sure the clutch is fully locked-up to the compressor when the AC is on. The lock sensor generates an AC voltage as the clutch turns and sends that signal to either an A/C amplifier or ECM (depending on the car model). The signal is compared to engine RPM and that’s how the system knows that the AC clutch is slipping.

Diagnose Toyota AC light flashing

So the first question you have to solve is what’s causing the AC clutch to slip. The first thing to check is the belt tension. Check to see if your engine is equipped with an automatic serpentine belt tensioner. If so, read this article on how to check the condition of a belt tensioner. If your engine has a manual tensioning device, check the tension by pulling up and down on the belt to gauge belt deflection. If it’s more than 1/2″ it’s too loose.

Next, check for poly-rib belt wear using a belt wear tool. You CANNOT gauge poly-rib belt wear visually. Read this post on how to measure poly-rib belt wear. Trust me on this.

If the belt is properly tensioned and in good condition, you’re next step is to check the AC clutch

Other causes of a Toyota AC light flashing condition

The AC clutch works with an electro-magnet. The AC clutch coil can burn out, short out or sometimes even become too weak to engage properly. However, those same symptoms can appear if you have a pitted AC clutch relay. So your first step is to use a jumper cable to provide battery power and ground directly from the battery. Hotwire the AC clutch and start the engine. If the Toyota AC light flashing condition disappears, replace the AC clutch relay. If the AC light flashes, make sure the magnetic pickup inside the compressor is still in place. Sometimes they can fall out.

If you still have the Toyota AC light flashing condition, replace the sensor

© 2012 Rick Muscoplat