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a/c mystery

gman7363 on Wed July 18, 2012 2:14 AM User is offline

Year: 2004
Make: Chev
Model: Express van
Refrigerant Type: r134a
Ambient Temp: 83
Pressure Low: 35
Pressure High: 425
Country of Origin: United States

Hello, have a strange problem on a 2004 Chev Van, originally an a/c line got a hole rubbed into, causing freon loss. Replaced hose,vacuumed down and recharge. Duct temps show starting to cool for about 2 min, down to around mid 60s, and then warm up higher than ambient (around Low 80s),compressor running fine, and then Hi side starts climbing to 425+ while Lo side remains around 35.
Seems like a blockage, checked everything replaced OT still doing same thing. Evap inlet was slightly bent, thought this was the was not. I then replaced every component, compressor, (twice)drier, condenser, all new a/c lines, evaporator and all new switches. still does same thing, gets cold for 2 minutes, the heats up for good. I also checked for another possible OT, none, checked for blocked a/c lines, blend door issues, temp control, nothing, everything working as it should , I also have reclaimed / recharged four times, trying by scale, and regular pressure methods, and every time it goes back to the same, cool first and then get hot. thanks in advance.

GM Tech on Wed July 18, 2012 5:29 AM User is offline

No mystery here... Did you ever consider replacing the fan clutch? High head pressure is due to lack of air flow across condenser- try spraying a garden hose on condenser see what happens to head pressure and cooling.

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......

gman7363 on Wed July 25, 2012 12:28 AM User is offline

GM tech , thank you for your prompt response, I considered the fan clutch, but it was less than two months old, so I gave it the benefit of doubt, returned it under warranty, Installed new one and mystery solved. 42 degree duct temp on 84 degree day, thanks again.

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