So on occasion the Air Conditioning light starts to blink on and off and the cooling stops. Fan still goes. Cycling the fan, the AC button, and the recirc/fresh air button a few times fixes it. Might take one attempt, might have to try it a few times/wait 5 minutes, then the AC runs fine and nice cold air. Eventually it will happen again.
Gauge on low side reads in the green nicely.
Anybody know what might be the cause and/or fix?

Lots of possibilities on this one. Mostly the ac will trip out if the limits on pressures are hit.

1] Improper amount of refrigerant in the system.

2] Condenser in front of the radiator plugged.

3] Compressor worn out and not working properly.




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A couple things to check:

When it quits cooling, is the compressor clutch still engaged?
Is the low-side reading still in the green when it quits? If you happen to be using a can with the gauge, they're notoriously inaccurate.

What are your high side and low side pressure readings? Does your condenser look clogged?

Good question. Guess I'll have to run the A/C in the driveway to try to replicate the scenario.

Good point. Am using a hose with the gauge that connects to cans, though it has never been refilled. Is what you're looking for, a 'marginal fill'?

Somehow the AC system 'knows' when there is not enough freon and shuts off the compressor (on my other toyota). How does it know that?

It does not, however, blink the light on the other vehicle, it shuts off the compressor but the AC light stays on.

Is there another scenario where maybe the fins are clogged up and just not providing enough heat exchange capacity, somehow 'fooling' the system?

BTW, it does run 'cool' when it is actually working.

Answers in Bold. Having your actual low and high side pressures would be helpful. Also when you are checking pressure the ac should be on, recirculate on, blower motor on high, coldest temperature selected, all the windows down, and engine at 1500 rpm's.

I'd look at the expansion valve as possibly being faulty.

Is the ac belt good. In most cases the clutch is slipping and that's why the light blinks.
edit: make sure the ac button is good since you said cycling it gets it going.