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hello,
i have a 84 k5 blazer that want to convert to R134a. replaced the compressor and the accumulator, flushed the evap, condenser and o-rings. question how much pag oil and freon do i add?
thanks, sendo
 

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New compressors typically come with the oil fill. Unlike R12, the oil migrates with refrigerant, most remains in the compressor.

Charge based on mass of refrigerant if the conversion kit specified. Otherwise, you must fill based on the two pressures, compressor suction and discharge. 25 to 50 PSI low from 70 to 100°F are typical low side pressures. 145 to 315 PSI at 70 to 100°F. Pressure is based on open doors, open hood, engine at 1500 RPM.

You must have a manifold gauge set, this is the only safe way. And you must evacuate the system fully. If the system has been open for more than a few hours, you must flush all lube oil, clean and dry. Then replace oil with recommended PAG , evacuate and charge.
 

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1997 GMC K3500 dually 4L80 4x4
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I would think the compressor came with 3 oz probably pag46. Although it should be blue pag 150. I allways go with the old school 6 oz for a compressor, so add 3, 2 for condenser, 2 for accumulator, 2 for evaporator. or, total of 9 oz for those older systems. We used to put a bit less 134 than R12, but the last ten or fifteen years, I've been filling them with the specified amount of 134 that is recommended for the R 12. In your case 3 lbs. Make sure you get a good vacume for at least an hour on the system before filling, or you'll have air and moisture issues later.

Good luck

Mac
 
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