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A/C freon discharge - white smoke and hissing noise

randolphoralph on Fri September 04, 2015 4:06 PM User is offline

Year: 2003
Make: Chrysler
Model: PT Cruiser
Refrigerant Type: R134

I am having issues with the A/C on my 2003 PT Cruiser.

About a month ago I started my car and it was idling with the A/C on. All of a sudden I heard a hissing noise and a cloud of what I thought was white smoke poured from under the car. Not knowing what was wrong I turned it off, and checked under the hood. I could not see anything wrong so I started the car again and within seconds the hissing noise returned with the white smoke. Then the problem stopped. I noticed that the A/C was not as cool as normal. In researching online I found that what happened was that the compressor discharge the freon. I took the car to a mechanic who said it was about 1 can of 1 3/4 cans low on freon. He filled back up with freon and the problem did not happen again after testing it for two days. He informed me that most likely the freon discharged because the pressure build up to much as a result of the radiator fan not kicking on. He check the fan and it worked fine so he replaced the fan relay just to be on the safe side. After getting the car back the air coming out of the A/C was cold but not as cold as I remembered it being before the problem. After asking the mechanic he told me he only filled it to the proper level so I let it go. For the last three weeks I have had no issues.

Today, I got in my car and got about 1/2 mile down the road to a stop light and the hiss started with white smoke again. Except this time there is no cold air blowing out.

I spoke with the mechanic and he is still thinking that the cause of the discharge is the radiator fan not coming on.

I am not an expert when it comes to A/C systems but even if the radiator fan is intermittently not working wouldn't the high pressure switch on the A/C compressor prevent the pressure from building to the point of a freon discharge?

What am I missing? Is there something else that could be causing this?

I worry if I take it back to the mechanic that he will put more freon into it and test the system and not find anything out of the norm until it discharges the freon again.

Edited: Fri September 04, 2015 at 6:41 PM by randolphoralph

GM Tech on Fri September 04, 2015 4:31 PM User is offline

The switch (or more likely pressure transducer) will shut off compressor IF it is mounted upstream of the blockage or inadequate condensation issue. If sensor is after the condenser, and blockage is in front of condenser or in the condenser as yours seems to be, the sensor doesn't "see" the high pressure. Heck the problem could even be internal to the compressor and the discharge port blocked from the inside, - no sensor can catch that one. The fact that the sensor does not catch it, is your mechanic's first and foremost biggest hint as to the cause of the problem.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

randolphoralph on Fri September 04, 2015 4:52 PM User is offline

Thank you GM Tech!

So if I understand your are indicating that the cause of the issue could be a blockage or inadequate condensation issue versus high pressure caused from inadequant cooling.

I am so confused as to why the problem would take three weeks before occuring again.

I have to apologize if I seem limited with regard to knowlesge of A/C systems. While I am very familiar with car mechanics I have very limited knowledge on A/C systems or how they operate.

mk378 on Fri September 04, 2015 4:52 PM User is offline

I'm not sure if this is the case with your car, but late model cars usually have a sensor to read the high side pressure and feed that information to the PCM. The PCM then uses the same sensor to make two decisions:
> 250 psi or so, fans on.
> 450 psi or so, shut down compressor.
Now imagine that the sensor falsely reports a low reading to the PCM. Not only will the fans not start, but the over pressure shutdown doesn't happen either. The result is the relief valve pops when you get to a stoplight.

A good scan tool can look at the reading from the sensor and see if this is the problem or not.

randolphoralph on Fri September 04, 2015 5:09 PM User is offline

mk378 I am not sure if a 2003 PT Cruiser has a high pressure sensor. I did notice a sensor on top of the know there is a sensor on the top of what I believe is the accumulator (round container mounted to the firewall).

TRB on Fri September 04, 2015 5:17 PM User is offlineView users profile

PT Cruiser has a HI Pressure cut out in the compressor.

Switch on accumulator is the low pressure cycling switch.


When considering your next auto A/C purchase, please consider the site that supports you:

randolphoralph on Fri September 04, 2015 5:24 PM User is offline

Thank you TRB for the link.

It sure would be nice if $11 part and some freon will resolve the issue.

So if you had to place money on a the cause would you start with the high pressure cut out?

TRB on Fri September 04, 2015 5:30 PM User is offlineView users profile

Even if the switch is allowing the system to reach a pressure that the relief valve is opening. You still have to find the reason for the high pressure. Which most likely is a fan issue. The previous posts have listed some things to check.


When considering your next auto A/C purchase, please consider the site that supports you:

Jag987 on Fri September 04, 2015 6:29 PM User is offline

Maybe it is just me, but if your mechanic is measuring how low the charge in yours system is in terms of cans of 134, maybe you need to find a new mechanic.

I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

randolphoralph on Fri September 04, 2015 6:39 PM User is offline

I did not even think about the issue being caused by the switch allowing the relief value to open and a secondary issue causing the high pressure. Ok so check the sensor, the fan, and possibly a blockage.

Unless anyone else has any thoughts I will wait and see what the mechanic finds.

Thanks all.

randolphoralph on Fri September 04, 2015 6:48 PM User is offline

Jag987 my mechanic referred to cans of 134 because when I asked how low it was I asked how many cans of 134 he had to put in. My mechanic laughed at me and humored my lack of knowledge by telling me the entire system did not require "cans" of 134. So he told me it was only 1 can low.

I am sure he is not truly measuring it using cans for a measure.

Edited: Fri September 04, 2015 at 6:50 PM by randolphoralph

randolphoralph on Wed September 09, 2015 5:44 PM User is offline

Well took the car to the mechanic and after a full day of testing the mechanic was not able to get the freon to discharge again and each time the fan kicked on. He stated the switch did not appear to be bad. The mechanic is at a loss and says at this point we would be throwing money towards parts to fix it. My mechanic told me that he is not the mechanic just to throw money at a problem without knowing what the problem is. He had refilled it with freon to test it.

I am going to pick up my car. I think I will start by replacing the fan and the high pressure cut-out switch.

Does the freon need to be captured before replacing the cut-out switch?

Is it possible that the high pressure switch or fan is failing intermittently?

How can I test the switch?

Edited: Wed September 09, 2015 at 6:01 PM by randolphoralph

mk378 on Wed September 09, 2015 8:21 PM User is offline

You may want to change the fan relay, sometimes when a relay is almost worn out they don't always make contact.

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