Question about 1999 Chevrolet Suburban

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I have a 99 chevy suburban that won't cool past 60 degrees and when idling is at 70 degrees. I have replaced the a/c compressor, orfice tube,the accumilator,rear expension valve, and fan clutch. My low side pressure is 70 PSI and my high side is 300 PSI. Our humidity here is about 80%. The heat index is about 102 degrees. I can't figure out whats wrong. Got any ideas?

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These numbers are a little high depsite the high ambient conditions.Amazingly enough ,automotive low side suction pressure will equal the degrees its putting out at the evaporator coil...for instance,70 psi low side pressure will produce about 70 degrees of cooling. At 300 psi on the high side(which is high) this is about as low as the suction pressure will go....you need it to go lower.I would probably be concerned with the freon level as a slight overcharge could boost these numbers.Poor air flow through the condenser can also create a higher head pressure than desired.If possible,I would evacuate and re-charge the system with the correct amount of 134a refrigerant. Try to get those pressures lower...about 250/50 would be a decent pressure value in this ambient condition.Verify good airflow through the coils and pay close attention to any foreign debris like plastic grocery bags or wrappers covering the coils...Ive even seen these make their way between the small gap between the condenser and radiator so use a light and inspect carefully for this.Air flow through that condenser coil is vital and any deficit there will create high head pressure which obviously causes high suction pressures....good luck

Posted on Jul 29, 2009

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your low for 134A should not exeeed 45 Psi and highs for 134A shouldent get above 300. When your replacing stuff are you cleaning out the residue from your evap and condensor prior to reinstalling Freon?allso adding oil. and vacumeing your system prior to charging helps to get all the moisture out. In high humidity its crutial for optimal cooling and when system is open to the humidity for some time it gets loaded with water and vacuming can sometimes take as long as 10 hours

Posted on Jul 30, 2009

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