Automotive Air Conditioning Information Forum (Archives)

Metal Man on Wed June 13, 2012 8:36 AM

Year: 1998
Make: Chevy
Model: Silverado
Engine Size: 5.7
Refrigerant Type: R 134a
Ambient Temp: 88
Pressure Low: 55
Pressure High: 115
Country of Origin: United States

He guys, Had a customer bring a 98 Chevy Silverado in with no AC. System had no refrigerant at all. At some point the Compressor and Accumulator have been replaced.Both still look nice and clean.

The leaks were easy to spot. Someone cross threaded the suction line at the accumulator, reused the sealing washers at the compressor and reused all the stock o rings. Plus the orifice tube was nasty.

After replacing the lines, o rings, sealing washers,orifice tube,and accumulator I evacuated the system and charged 2LB of refrigerant these are the pressures i get. Ac at max. Condenser has good air flow and clutch fan works good.

At idle 55 on Low side - 115 on High side with lots of gauge fluctuation. Ambient temp at 88. Vent temp in low 60's
At 2000 rpm 35 on Low side - 150 on High side with little gauge fluctuation. Ambient temp at 88. Vent temp about 50.

Is the compressor going out? Its a replacement compressor. Sadden is the name on it.

HECAT on Wed June 13, 2012 12:19 PM

Do you have the full charge in it? A quick look says a 98 full size truck calls for 32 oz.

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Metal Man on Wed June 13, 2012 9:55 PM

Yes it has a full charge. I vacummed the system for 1 hour then added the required amount of 2LB 0oz ( 32oz) of R134a.

ice-n-tropics on Thu June 14, 2012 4:23 PM

MM
Fantastic young buck!
At 55 MPH, 88F ambient, in the max (recirculation) AC control panel setting, central louver temp should be cycling at least down to 45 to 50 degrees (after 5 min.) w/ the Sanden drop in replacement compressor (if the oil quantity is not over 8 oz.).
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Fri June 15, 2012 at 5:01 PM by ice-n-tropics

Metal Man on Thu June 14, 2012 9:30 PM

Hotrod the AC works decent while the truck is moving. Cooling falls off at idle though and picks back up at high way speed. That combined with the low high side pressures and gauge fluctuation is what had me thinking the compressor was on its way out.

ice-n-tropics on Fri June 15, 2012 4:59 PM

MM,
If the condenser air flow can be blocked with cardboard until the discharge pressure reaches 300 to 350 psi, then the compressor is AOK.
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Metal Man on Fri June 15, 2012 9:05 PM

Thanks, i'll try that next time he brings it in.