AC suddenly quit AC-ing

[iBooger]

Firstly, I'm an OK mechanic but an AC dummy, so anything I say from this point has a good chance of being stupid. You've been warned. 🙂

Step-son's 2004 LS430 AC all of a sudden quit blowing cold air. Turned the car off to go to the dog park for an hour, came back and there's air blowing but it's warm. He said it was working fine before. Cabin filter is good, both fans in the engine compartment are working. We put one of those refrigerant re-charge cans with a simple analog gauge on the low-side port and it reads high (i.e., in the lower part of the red zone; 55-ish pounds if I remember correctly) with engine at operating temp and AC turned on max. Didn't add refrigerant, of course, just used it for the gauge. Compressor clutch on AC pulley appears to be turning, but never turns on/off. Checked the AC fuse in the interior fuse box and it's good. Looked in the engine compartment fuse box but couldn't see anything labeled "AC" or similar.

The fact that it happened so quickly *tends* to make me think it's not a leak. Would like to save him some $$$ and fix this myself, so does anyone have any advice on where to start looking? Maybe a sensor or relay somewhere? Thanks in advance!

[RX400h]

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