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1997 Suburban with dual A/C

Scout3 on Sat August 16, 2008 12:09 PM User is offline

Year: 1997
Make: Chevy
Model: Suburban
Engine Size: 5.7
Refrigerant Type: 134
Ambient Temp: 83
Pressure Low: 40
Pressure High: 155
Country of Origin: United States

Advice please. I am trying to help my neighbor. He has 97 Suburban with dual A/C. He had it parked for about 2 months due to gas prices. Used it yesterday no cold air. He had the system completely rebuilt about a year ago and will be taking it back Monday. He needs to use it Sunday and I am trying to help him get a little cooling. I hooked up my guages and read nothing. Pushed in on the valve on the high side and got the slightest little puff. Assumed total loss of freon. Started engine and turned on A/C and to my surprise the compressor engaged. Lo side showed vacuum and cant remember Hi side. Put two 12oz cans of freon in. Low side reads 40psi and Hi side about 155. Reved engine and lo side dropped to 16psi and hi went to 165psi. Air temp has dropped only a little from 82 degrees to 78. My book states normal readings lo 28 and hi of 320. My questions are:
1. Are reading done at idle or fast idle?
2. What are the correct pressures for a dual A/C system?
3. Should I add more freon?

Thanks for any help. He will be taking it back to his mechanic, he just needs some temporary relief.


chris142 on Sat August 16, 2008 4:35 PM User is offline

Readings should be taken @ 1800-2000 rpm.

Total charge is somewhere around 3.0-3.5 lbs but I don't remember the exact amount.

High side pressures should be 250-275ish. Low figgure around 40 with both units on full blast. Fan clutch must work properly.

Check the aluminum lines that go to the rear unit for a leak where they rub together near the front wheel.

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