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Speeding up a compressor with a smaller pulley?

chris142 on Sun June 09, 2013 11:12 PM User is offline

Year: 87
Make: ford
Model: f250
Engine Size: 420/6.9L
Refrigerant Type: r134a
Ambient Temp: 100+
Pressure Low: varies
Pressure High: varies
Country of Origin: United States

Hey guys this is on my personel truck. My original FS6 compressor sprung a leak so I replaced it with a Look alike Sanden thing. It's basically a sanden guts in a body that will bolt where my FS6 was.

At idle the compressor is turning too slow. Rev it up and it works great! @ idle the low side will go up to say 70psi and the high side will drop to say 125-150. Rev it up and it goes to 30/225 and blows cold in the cab.

IMO I need a smaller pulley to speed the compressor up. Any ideas?

Cussboy on Mon June 10, 2013 4:42 AM User is offline

Is your fan clutch OK? Sure it's not a condenser cooling issue?

GM Tech on Mon June 10, 2013 7:57 AM User is offline

smaller pulley will NOT help that big of a pressure swing.

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......

chris142 on Mon June 10, 2013 3:01 PM User is offline

Fan clutch is a screamer. I threw it into neutral @75 mph on a downhill and the temp out of the vents got warm. Tevving it up makes it cool plus if it was an air flow problem the high side pressure would go up @ idle not down. I think I'm going to go back to an actual fs6.

chris142 on Mon June 10, 2013 3:02 PM User is offline


chris142 on Mon June 24, 2013 11:50 PM User is offline

Update. seems that my compressor slowly lost it's ability to move refrigerant. It was ok at high speeds but would not pump well @ slow speeds/idle. Happened so slowly that I didn't notice the change until it was too late.

No junk in the orifice tube.

I went ahead and rebuilt the whole thing with another new compressor, dryer, flush etc. I went with PAG46 this time. Last time it was Ester. We will wait and see how long this one works.

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