whenever I drive my truck when it really hot, like 90 F + and I park it in a parking lot, shut it off, go inside, then come back outside and start it and let it idle for a few minutes- it leaks out freon until I shut off ac control switch. it seems to be blowing off like a release valve

it only does this when hot outside and parked at idle . it has never done it while driving or when throttle is reved some. otherwise no leaks.

this has happened a few times, and i need to add some r-134a afterwards

what needs replaced?

 

How do you know it's leaking freon?

 

it makes a loud hissing noise like a pressure relief valve on an air compressor, it looks like steam coming from under the hood, and you can smell it.

it is also low on freon after it happens and the AC won't get cold.

that's how I know

 

Anyone Got Any Ideas On This?

 

dnvoss, wish I could help. im having the same problem, happened 2 times last year and once this year. this year I have a new compressor, accumulator, and orfice tube, and had the same thing happened. if anyone knows any thing please help. called local dealer and they were no help, said they would have to see it to diagnose. strange thing is i do alot of idling and it doesnt do it all the time. just 3 times now.

 

The head pressure is getting too high. There is a pressure relief valve. There should also be a high pressure cut out switch.

Most likely cause is a poor operating fan clutch. This would especially be noticeable at idle on hotter days. Look at the fan and see if it is spinning much at all at idle. It should be moving some air. If it is really bad it will be almost still. The proper charge is also critical.

 

Correct the problem is high head pressure resulting in the relief valve venting to prevent blowing the lines.

Causes of high head pressure.

• Moisture in the system
• Plugged screen in filter
• plugged orifice tube or expansion valve (depending on design)
• Heat build up due to poor heat transfer at the condenser (fan or trash on fins)
• Too much freon in the system. ( do you have gauges for low side reading)

My question .. was the receiver dryer ever replaced. If the dessicant is fully depleted you might have moisture in the system.

If you had service did they install a new orifice tube.

Check the condenser to make sure it is clean.

Hope these help you on the right track.