Help me diagnose A/C problem

[UnhandledException]

Car has 47,600 miles. A/C compressor was changed around 5,000 miles when I found a massive green puddle on my garage floor (there were no symptoms, it just went boom on its own). Anyways, that was 2.5 years and 42,500 miles ago.

This summer, it started blowing hot air only when intake air temperature reaches and exceeds 115F. This is true REGARDLESS of whether the car is idling or not. For example, I can idle for 30 minutes without a problem if outside is 70-80F and IAT never reaches 115F. Or I can have the problem while cruising if IAT exceeds 115F like it was the case today. Today it was 106F outside and the A/C went on/off even while cruising on 6th gear.

What could this be?

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[Matthew]

I had a similar situation with a slow leak. Once the ac pressure gets below a certain point from low freon the system will not allow the compressor to kick on to save it from damage. It seemed that when it was near that threshold it would work randomly. Ended up having to have the dash pulled and evaporator replaced.

 

[torque124]

First thing buy a set of gauges and measure the pressure.... take it from there.

 

[The Chairman]

First thing buy a set of gauges and measure the pressure.... take it from there.

Agree. Too much pressure will also shutdown the system. Sounds like yours works fine at idle, etc. But when up to speed at high temps, its shuts down. My first observation would be that it has too much Freon. Put gauges on both sides and you will find out real quick if that is the problem.

 

[1Bad_ShelbyR]

Sounds like the High Pressure Safety Switch is cycling your compressor on and off

at high ambient temperatures

If no one has serviced the sealed refrigerant system lately ..........

Perhaps your condenser coil is blocked ............ therefore raising the head pressure

(high pressure) and tripping your safety control .......... check air flow across condenser coil

Either that or safety control is defective and cutting out to soon ........ Good Luck !!!

 

[HaleFire]

I had a similar situation with a slow leak. Once the ac pressure gets below a certain point from low freon the system will not allow the compressor to kick on to save it from damage. It seemed that when it was near that threshold it would work randomly. Ended up having to have the dash pulled and evaporator replaced.

This was my issue as well. First thing I noticed was the compressor kicking on/off at idle and the air was working randomly. Took it to dealer and they found an evaporator leak.

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