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V5 Refrigerant Control Valve; Replace During Retrofit?

retrofit on Wed August 22, 2007 3:47 PM User is offline

This question comes up sometimes because 4 Seasons (Factory Air) includes a tag with their pre 1994 application compressors that says

Quote
This compressor is equipped with an R12 Control Valve. If retrofitting to R134a, Control Valve 38846 is recommended for optimum system performance. GM may also have recommended changing the valve in some retrofit instructions.

The 4S part number crosses to GM 2724790 which is the R134a valve used in many V5's for about ten years, starting in 1994. I think the R12 valve is p/n 2724331. Noticed in the V5 parts breakdown at this site that two part numbers are listed, one for R12 and another for R134a but cant find a spec sheet for either valve. Anyone know what the difference is?

It seems that R134a can operate at a lower suction pressure before freezing the evaporator than R12 so there is no need to change the valve for that reason. Maybe you would get a slight improvement in cooling? I don't think the valve is changed during most retrofits.

JJM on Wed August 22, 2007 7:37 PM User is offline

You certainly did your homework, and are absolutely right. The control valve for R-134a destrokes the V5 at a lower pressure. And you're also right that the control valve isn't changed with most retrofits... and for that matter neither is the accumulator and in all too many cases the oil, but it doesn't make it right. The control valve should be correct for the application, either R-12 or R-134a.

By the way, I don't think GM recommends changing the control valve because they don't recommend retrofits to begin with.

I can see why you'd hesitate on replacing the control valve... at $120 or so list, they're not cheap.

Joe

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retrofit on Thu August 23, 2007 1:40 AM User is offline

GM also has a special PAG oil to be used when a R12 V5 is retrofitted to R134a. It's p/n 12346292, ACDelco 15-100 but at $1.25 an oz wholesale, I'll bet not too many use that either.

marvin-miller on Tue August 28, 2007 2:34 AM User is offline

Last year I did a job that got a reman V5. I test out all the cars I do on the road in npth city and highway. I found the vent temps to be terrible for a new compressor and was quite disappointed as the job had been a pill.

After thinking about it a bit I realized that the only thing it could be was the control valve. Like yourselves I looked one up - no stock and more then $100 :-(

I took a gamble on it and pulled the old one off the core and installed it in the reman compressor - bingo! Proper vent temps (like you should get with a new compressor). If I remember right the vent temps with the reman control valve were about 11c on the road and with the old unit it pulled down to 6c which is about what I usually see with reman compressors on most GM's.

So, just to give my .02 cents worth, I found the difference between the two to be very noticeable and comparable to and old comressor with lots of miles versus a fresh one.

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Best & Thanks;
Marvin

TRB on Tue August 28, 2007 12:50 PM User is offlineView users profile

Nothing really special about the PAG Blue.

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