Aircon behaviour - low gas

[rusty0273]

Can anyone advise what to expect when the aircon runs low/out of gas?
I have a leak which I intend to sort out with a new condenser.
However, currently, if I press the Aircon button while the car is running nothing happens - no led on the button and the compressor does not appear to engage. I am hoping this is designed to happen automatically when then the refridgerant drops below a certain level and there's not another issue with the system. Could be as simple as someone's removed the fuse but I'd appreciate any guidance of this is normal or warrants further investigation.

[ucb]

NO idea re the MR2 but my old Volvo would not engage the compressor if the HAVC system pressure was low.

[Bossworld]

You should hear the revs rise and drop if it's running properly, and the click of the compressor coming in.

There is a sight glass under the frunk cover which I believe should be clear and bubble free when the system is operating properly.

It's a very basic system so I think it coming on/off every 30 seconds to a minute is normal to prevent icing and reduce fuel consumption.

There is a pressure switch, I was under the impression under low pressure (e.g when my knackered condenser was empty) the light still came on but no cold air came out. If the compressor is faulty you should get a blinking yellow light. No light at all sounds suspect.

Really, you need a local A/C specialist. It's not a complicated job and I helped fit the replacement condenser with my local chap, but in terms of gauges and what to look for, ideally you want their expertise. Alternatively you want the official Toyota air con documentation from the service guide which explains the pressure readings.

Tagging @mulaz as he knows more than me.

[rusty0273]

Thanks for the responses. Just for clarity, the aircon has never worked in my ownership so I don't know with any certainty that's its just the leak that's the problem. I'll have the condenser fitted at a local garage that does aircon work and can check it all out but any reassurance on the button LED would be appreciated.

[Ardent]

You should hear the revs rise and drop if it's running properly, and the click of the compressor coming in.

What Bossworld said. ^^^^ should happen when you push the button.

[Bossworld]

Thanks for the responses. Just for clarity, the aircon has never worked in my ownership so I don't know with any certainty that's its just the leak that's the problem. I'll have the condenser fitted at a local garage that does aircon work and can check it all out but any reassurance on the button LED would be appreciated.

As per post above I'd expect either the light on (with or without cold air depending on the charge state of the system), or a blinking yellow light (compressor failure).  No light at all sounds like a relay or fuse gone, but I'm no expert.  That said, it doesn't appear to be listed in the Toyota troubleshooting steps for A/C.

[rusty0273]

Thanks all. Sounds like I need to do a bit of investigative work on the system.