It's telling you the revolution sensor is not matching the revolutions of the engine. The ECU takes over and cuts current to the AC when this happens and the ac light will start blinking. A turn the AC of then turn it back on and it's not blinking tells you the problem is going to lead to no AC if you don't get it fixed.
what cause the ac light to blink on a 1999 Toyota sienna
If the AC light is blinking in the Toyota 98 Sienna, it means that something is internally wrong with your AC, it has stopped working, and it is recommended that you take it to the dealer to repair. This is not a very specific answer, but that is exactly what it says in the user manual. I find if I stop, turn off the car and AC for about 15 minutes, then restart, it will work again, until a week later and I have to repeat the process.
I believe it is blinking because there is a misfire inside the engine. Meaning that the timing is off. This could be because the timing belt may be old and the teeth are chewed and are not as rigid. That was the case for my 96 tacoma.
My family has driven three hours on empty in a 1999 Toyota sienna. We were driving on the mountains, and we thank God to be alive.
The gas cap was loose on my '04 Sienna. How's that for simple...
If an AC light is blinking on a 1991 Toyota Camry it may indicate that a belt is slipping. The AC light may also blink indicating that the system has been overcharged.
If the tail light on the passenger side of a 1999 Toyota Sienna CE is out, it is most likely a blown bulb. The bulbs can be purchased at any auto parts store.
The problem with your air conditioning light blinking in the 4runner is a bad relay. Toyota has updated the relay to part #90987-02028. Call your local Toyota dealership for this relay. You can buy it at the parts counter. It is about $65. It takes 1 minute to replace. This same procedure is for the Camry and other Toyota models with the same blinking AC light, but the relay part number might differ.
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A failing alternator.
Tire pressure warning light
The A/C light blinks because the A/C computer is not "seeing" the compressor shaft turning. Probably a relay fault but could be a bad mag clutch, broken wire, siezed compressor, faulty compressor speed sensor,,,the list goes on and on.