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The A/C light flashes because the compressor is not turning or the belt is slipping. The speed sensor in the compressor is not matching the speed of the engine. Check the connectors to the A/C compressor and for broken wires to the connector and the belt tension. There have been some issues with the magnetic clutch relay on some Toyota models up through 04. You could try swapping the mag clutch relay with the horn relay I believe it is the same configuration, as a test. If you need a wiring diagram let me know.
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