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High readings for low and high sides

Godzilla on Wed June 16, 2010 9:51 AM User is offline

Year: 1984
Make: Nissan
Model: 300ZX
Refrigerant Type: R-134a
Ambient Temp: 78+90
Pressure Low: 50
Pressure High: 275
Country of Origin: United States

I converted my system from R-12 to R-134a about seven years ago, and it's worked fine since. After my original unit froze up last week, I installed a good, clean used OEM wrecking yard compressor (I removed the unit myself, lines were clear, I immediately plugged the ports to prevent contamination).

After installing, I put in 4oz Ester oil, evacuated the system, then charged with 2.4 lbs of R-134a (the recommended amount in the car's shop manual.) The a/c works great now, but I note the low side is 50lbs, high side 275lbs (at 70 degree outside air temp, and the same a few days later when I rechecked it with outside air temp at 90), which seems a bit high for an automotive a/c system. What do you think?

Thanks for your help!

TRB on Wed June 16, 2010 11:28 AM User is offlineView users profile

If all you did was swap compressors. Adding another 4 ounces of oil may have been too much. But its hard to say what's going on as this is a conversion and normal numbers will not be a factor per refrigerant amount.


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JACK ADAMS on Wed June 16, 2010 11:43 AM User is offline

You installed the R-12 charge amount, for a 134a conversion you will need to go 80% of the R-12 amount. This could be on of the reasons you have high pressures.

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