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96 suburban AC problem part 2

torque395 on Thu July 16, 2009 11:45 PM User is offline

Year: 1996
Make: Chevrolet
Model: Suburban
Engine Size: 6.5L
Refrigerant Type: R134a
Ambient Temp: 81
Pressure Low: 33
Pressure High: 260
Country of Origin: United States

My AC is still not working right. 81 degrees outside (with a killer 78% humidity) today when i took these readings. At idle speed, 600 rpm for the diesel, pressures are 55 low 260 high. At close to 1500rpm (very sensitive electronic throttle on this engine, its hard to get it right on) the pressures were 33 low, 260 high. Vent temp 58 degrees. Ive cleaned the condenser and radiator very well and this did improve the engine cooling as well as the AC cooling but its still not right. What i *expect* is about 45 degrees while driving and maybe 50 while idle at a stoplight. Maybe I'm expecting too much, I don't know. After water on the condenser, pressures were 30 low and 145 high @ 600 RPM (it did drop significantly but it took it a minute) and at 1500 rpm the pressures were 28 low and 160 high. Vent temp still only 52-54 degrees at 1500. It sounds pretty good to me except for it not cooling at idle very well. It can easily get a 70+ degree vent temp at idle on a hot day. The clutch fan works fine as far as i can tell but it still acts like an airflow issue. The fan does not spin on residual energy, you take your hand off and it stops turning instantly. At 210 degrees it kicks on full blast and roars like crazy. It does not roar on engine startup tho as i've heard some say it should. Nothing would surprise me with the number of miles this truck has on it (250k) but it seems to work fine.

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

Cussboy on Fri July 17, 2009 6:59 AM User is offline

Subs of that vintage typically cool pretty well (min'e a '94, and I'm in Arizona. Sounds to me that your condenser is getting enough cooling, and when you cool it with water your high pressure reading is low. How much R134a was added last time it was filled? I think you have two issues: (1) air flow or condenser issue
(2) R134a a little low, possible due to underfill or a leak.

Don't just add refrigerant, or your pressures will be too high, you could cause damage. So address (1) first.

torque395 on Fri July 17, 2009 10:46 AM User is offline

What kind of condenser issue would it be if it isnt airflow?

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

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