Hello Corvette fans, I am French and having no answer on the French Corvette forums about my problem, I need your help.
Sorry , i didn't found where i can present me.
my English is very bad and i need some help from a friend to post .

My problem is : I have had my air conditioning system redone on my Corvette C4 1992: new compressor new condenser and new drier bottle. No leak on the circuit, system charged with 1 kg r413a.
I was happy everything was ok the compressor worked well , the clutch also, but driving back home after 35 miles it went wrong:
With air conditioning on automatic , and temperature on 90° F the compressor never stops and the drier box and the hoses are covered with ice.
What I don't understand is that on low and medium vent ,or deice windscreen the compressor doesn't stop running.
On medium vent or low vent the compressor doesn't run at all being on 59°f or 90°f.
I had HEATER/AIR CONDITIONING CONTROL-ELECTRONIC , changing it ,the problem still remains.No error code on the module.
Could it come from a AIR CONDITIONING REFRIGERANT PRESSURE SENSOR SWITCH ?
Thank you very much for your help
Sincerely

Pascal

 

I would re check the refrigerant pressures.

 

The gas pressure is good; the circuit was verified with nitrogen in 15 bars

 

how many lbs is 1kg?

never mind it's 2.2 lbs

 

1 KG = 2.2046226218487757 lbs !!!!

 

A photo of my country with my little c4 in the background :+



: Cheers:

 

Which is 217PSI!!!! You need to find someone who has a set of A/C manifold gauges. The compressor could run all the time if the pressures never reach the low cut off point. High pressure cut off is at 430psi +/- 20psi. Low cut off is 44 psi. This pressure sensor is located in the evaporator tube. Also, you could have a restriction in the system, it should not ice up. You definitly have a problem. If you do not have a Field Service Manual (FSM) for your 92, it is advised you obtain one. The info I posted is from a 93 manual which will be similar.

I suggest you find a local mechanic to you, A/C systems are typically just A/C systems. Nothing crazy about it.

Also, anytime you have the system in auto, norm, bi-level, or defrost the a/c compressor will run, it should not run in the floor position.

Hope this helps, good luck.

 

Thank you for your answer; It confirms a problem of pressure sensor;
I saw these 2 sensor; I am going to make verify the pressure; I don't know if this sensor is a standard part or if it is necessary to order in the USA ?
Sincerely

Pascal

 

Here's a chart showing the temperature and pressure
relationship for different refrigerants.

http://www.benbooysen.co.za/conversi...eTempChart.pdf

Your 92 Corvette originally used 2.25 lbs. of R12.

When you retrofit from R12 to R413a the manufacturer
says to use 90 percent of the original refrigerant amount
which would be 2.0 lbs.

The Low Pressure Cycling switch keeps the refrigerant from
freezing

R12 Low Pressure Cycling switch.
Opens 170 kPa = 24.5 psi
Closes 317 kPa = 46 psi

R134A Low Pressure Cycling switch. (R134a was used starting
in 1994 model Corvettes).
Opens 159 kPa = 23 psi
Closes 317 kPa = 46 psi

The chart shows R413a freezes at 272 kPa = 39.45 psi.
So if the compressor is not shut off before the low
side pressure reaches 272 kPa the evaporator will freeze.

Here's a picture of a 93 Low Pressure Cycling switch.



1992 and 1993 models used used the same Low Pressure Cycling switch which some people have said was not adjustable.

Some people have said 91 and earlier Corvettes had an adjustment screw that could be turned to vary the cut off point
of the Low Pressure Cycling switch.

So the question is, could you use/install an earlier adjustable
Low Pressure Cut off switch and monitor the pressure and
adjust the screw so the compressor shuts off before the low
side pressure reaches 272 kPa/ 39.5 psi?

 

If the hoses are ice covered you may have a clogged expantion tube which is located in high pressure line

 

Inadequate charge can also result in icing of suction lines.

 

Thanks for your response ; its not a problem of charge : i tried with 0,85 kg then with 1 kg of pressure and the result is the same . I,m actually in holidays ; i,ll see at me return
sincerely
Pascal

 

my 89 stuck on heat mode, discovered the programmer had two resistors loose in he printed circuit board....dont know that this is the same? spent $300 chasing other parts. finally took the programmer out and local TV shop repaired it in 10 mins...free.