AC light blinks on/off, stops cooling. Fiddle w/controls, works again eventually.

[5th4runner]

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?

 

[brillo_76]

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.




Sent from my SM-J337V using Tapatalk

 

[azrex]

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?

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.

 

[Bad Luck]

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?

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

 

[5th4runner]

A couple things to check:

When it quits cooling, is the compressor clutch still engaged?

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

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.

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.

 

[Bad Luck]

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?
There is a low and high side pressure switch to protect the compressor. If you don't have enough refrigerant it will cause the low side pressure to be too low and trip the low side pressure switch.

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?
If the condenser is clogged up it will cause the high side pressures to be higher than normal and could trip the high side pressure switch.

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.

 

[azrex]

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'?

Possibly it's low, but if it cools well except intermittently,
I doubt that the problem.

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?

There's a pressure switch that shuts off power to the compressor if the pressure is to high or low.

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

The blinking light alerts you that there's a problem and many Toyota models have it. Some Toyota compressors use a speed sensor that will disengage the compressor if the rpm of the compressor is out of spec with the rpm of the engine.

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

Clogged fins would create high pressure and the switch would shut down the system until the pressure dropped. With it working intermittently, I would be more inclined to look at the high or low side pressure when it quits. High pressure, probably over 375, the pressure switch would shut it off and if the low side is at zero or in vacuum when it quits cooling, the expansion valve is likely the culprit.

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

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

 

[spartacus]

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.