This chart was posted in another forum:
The person posting had purchased a new (replacement) V5 compressor and was wondering what the color of the valve indicated. The new compressor had an orange dot while the valve more commonly used (ACDelco 15-5452) valve has a brown dot.
I seem to recall that GM Tech mentioned once that the colors indicated different pressures used in the various GM systems. Does it make any difference?
The variable stroke compressor control valves are calibrated to destroke the compressor at the stated pressures-- this is to avoid evaporator freeze-up while maintaining maximum efficiency (cooling) The ratings are different because of the use on different systems- the destroke pressure on a Cavalier is different than that of a 4cylinder S-10...hence the different calibrated valves-- this is basically due to the pressure drop from the evaporator to the compressor (where the control valve is) which can be a function of the length of the suction hose to the compressor......so in short does it matter??? If in doubt- go with the higher set valve- you will always avoid freeze-up but will sacrifice so cooling ability--but will it be enough to notice??? that is up to you to decide....I used to fix freeze-up complaints (they usually came from humid areas) on S-10s by installing the next higher set valve-- worked every time.
Just remember- you can't blow air through ice!!!
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......
Nice response, may need to move this to the tips section in a few days!
Thanks for the quick reply, GM Tech. If you want to look at the other discussion thread, itÃ¢ÂÂs at the Fiero Forum. Lots of interest over there A/C maintenance and in conversion to R134a. Maybe some of them will be coming over here to look for advice. Thanks again!
A follow-up question:
4-Seasons reman V5 compressors for the Fiero state: "Compressor Equipped with R12 Crontrol Valve. Alternate Control valve required for R134a." (They spell like they rebuild.)
The reman compressors at AMA don't mention that requirement. Nor does GM in their retrofit recommendations.
The R134a valve recommended by 4-Season is their p/n 38846 which is the same as GM 2724790 or ACDelco 15-5452. It has a brown color dot which indicates a set point of 43 psi (42 - 44 psi).
The R12 valve is GM 2724331, ACDelco 15-5310. It has a orange color dot indicating a set point of 45 psi (44 - 46 psi).
The tolerances of the two valves overlap! Is it worth another $80 to change it?
Edit: Found the answer to my question on another board These are quotes by a former Compressor Product Manager for Four Seasons:
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