Rans

I have a 2001. My a/c freezes up and the air blowing out the vents gradually decreases untill there is very little air coming out of the vents, even tho the fan is still running on high. The compressor is not cycling on and off, just staying on. Does the 01 have a low pressure switch to cycle the compressor or does it have the variable stroke compressor that is supposed to run all the time the a/c is on?
It will run about 40 mins. before it starts freezing up. Any help would be greatly appreciated.
Thanks,
Rans

Cybermind

Sounds like low freon to me. There may be other issues but normally, freezing up is caused by low freon level. But, this also means you may have some sort of leak.

Rans

A vacum has been pulled on the system and freon replaced to factory specs. and no leaks. Mechanic told me it was the climate control. I am looking for other problems. I'm no a/c man, but I don't think it is the climate control, but I have been wrong before...Ha
I am just seeing if anyone has had this prob. and what they did to fix it.
Thanks,

Bill Curlee

FIND A NEW AC MAN! Climate Control can NOT cause the evaporator to FREEZE UP.

The Temp Control flaps either open or cover up the AC Evap opening OR open or cover up the heat Coil opening OR a COMBO of both to get temperate air.

There is an orifice restrictor tube in the high pressure Freon hose. It sprays liquid R-134 into the evaporator so it can flash into a GAS. If there is NOT enough pressure in the system, the liquid flashes too quickly and causes the evaporator to freeze the humid air onto the evaporator coil.

Read your DTCs and see if you have any related codes:

DTC P0530 A/C Refrigerant Pressure Sensor Circuit Malfunction
DTC P0531 A/C Refrigerant Pressure Sensor Circuit Range/Performance
DTC P0532 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage
DTC P0534 Air Conditioner Refrigerant Charge Loss



You need enough pressure in the system so that the liquid CHILLS the evaporator. NOT FREEZES IT! There is a VERY fine line between too much pressure and not enough. The service manual is very specific on high side and low side operational system pressures.

BC

Rans

No.... None of the above codes .... the only one I have is a seat control module. I have owned the car less than a year, (My first vette). I had the freon checked and it was good. Got up the next morning and the compressor would not come on. Took it back to the shop and it had a bad schrader valve. Replaced both of them, pulled a vacum, and recharged to factory specs. It cools great for about 30 min. then the vent air gradually decreases untill I turn it off a few mins. and let it thaw out. Then back to normal for awhile then the same thing over.

Forcedvert

Is it on recirculate or outside air? Cold inlet air will also lower evaporator temps. A restricted orfice can also cause low evaporator pressures and allow the refrigerant to boil well below freezing temp of water. The lower the pressure the colder the boiling point that is why a system low on refrigerant will freeze up eventually. What I don't know about car ac systems .....is the blended warm air mixed before evaporator? If it does you could try it on recirculate and raise temp to see if it keeps it from freezing up. Anything that reduces air flow will also lower evaporator temps. Also if your radiator fans are running when air is too cold it will lower head pressure which will also lower evaporator pressure. It's a simple system with many things that could cause the freeze up. Sorry I don't know more about the configuration and controls of auto ac or I may be able to make a better guess.

Oh and your first guess may be it, it seems to me if it is a fixed orfice it would cycle the compressor to keep the pressure in a certain range!

Bill Curlee

Great recommendations..
That was going to be my very next troubleshooting recommendation (clogged orifice tube) If you put it on the FRESH air (outside air setting, it may extend the time period of the freeze up due to bringing in more warm air from the outside.

BC

Rans

I don't need it for several months. Ha
Thanks to all who replied.
I would still like to know, does the 2001 have a compressor that is supposed to cycle or is it one of the varible stroke ones that does not cycle on and off???

Bill Curlee

If its running correctly,,, IT DOES NOT CYCLE! YES, it has a variable pressure system that allows to compressor to continue to run and not at full loads.

BC

Rans

Thanks, I will get back on the prob. when it warms up. Ha

tawc5

I have a 2000 with the same issues: Air runs cold for about 20 minutes, then the air volume gradually decreases to nothing. If I turn the A/C compressor off (pushing the A/C button) for about 5 minutes, the air starts blowing again. I can then turn the A/C compressor back on and it will blow cold for about 20 minutes before I have to repeat the above steps. Also, I have noticed it appears only to happen at highway speeds...not around town. I had the A/C system evacuated and refilled to specs. But that didn't seem to help. Thoughts?

Bill Curlee

Your charge is low enough to allow the evaporator to FREEZE the moisture in the air on the evaporator coils. Get the charge checked and properly adjusted and that will solve that issue.

BC

thorn92

I have a 2000 that does the exact same thing. Did you ever figure it out?

Bill Curlee

ITS LOW ON CHARGE or THE ORFICE TUBE IS CLOGGED!!!!!!!!!!!! Plain and simple. A set of gages will show you what the issues is!

VERY HIGH readings on the liquid line high pressure side and low suction side pressures ORFICE CLOGGED!

Low reading on high pressure side low readings on low pressure side low on R-134!

BC

thorn92

My guages show around LP 41 and HP 235. Those appear normal from what I've read yet I have the problem. Would you consider those readings high or low?

thorn92

Ok... I'm doing it once again. 80 degrees, 65% humidity...LP 55, HP 295. That was in the garage. Once outside it was LP 51, HP 265. I'm assuming those are both high readings? With the car turned off it's LP 97, HP 95.

gimp

I am not 100% sure what corvettes should have, but in my limited experience, you should be seeing closer to 30 / 200 than 50 / 300.

huesmann

According to this chart, at 80º and 65% you should be getting about 40 and 200 psi.

thorn92

Yeah, I'm thinking it's a bit over charged. But I don't think that's causing the problem so it must be a blockage. Thanks for the input!

BigGun

Replace the orifice tube.