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Dave Nova
Dave Nova, Chevrolet Technician
Category: Chevy
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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1997 Lumina 3.1 A/C system was not working. Charged to 30 ...

Customer Question

1997 Lumina 3.1 A/C system was not working. Charged to 30 lb on low side - will not attain higher pressure. Cooling is marginal pressure switch to protect compressor ok. Compressor new 24 mo ago, condenser new last summer, Do you think the orifice is plugged or partly plugged??
Submitted: 9 years ago.
Category: Chevy
Expert:  Dave Nova replied 9 years ago.

If the orifice was plugged up, you wouldn't have any cooling at all. Are you measuring the amount of refrigerant you are charging the system with? Having the correct amount in the system is critical. Too much charge can cause low cooling as well.

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Customer: replied 9 years ago.
used a brand new manifold guage set - before chg low side was 14 lbs - added 1 standard small can of 134a - system got up to 30 lbs. cooling now only to 60 degrees with outside air 80-85.
Expert:  Dave Nova replied 9 years ago.
You had almost no refrigerant in the system before you started. One can is probably about 14 oz. of refrigerant. (less than 1 lb.) The system capacity is 1.88 lb. You need to add more refrigerant(at least one more can). If the low side pressure is 30 psi, you should be able to add more refrigerant. With the engine running and system on add refrigerant to the low side only. The pressure inside the can of refrigerant is equal to the temperature of the can(80-85 degrees=80-85psi) The pressure of the refrigerant inside the can(since it is higher than the low side pressure of 30 psi) will push into the system.
Customer: replied 7 years ago.

Here is what we discovered in 2009 after deferring any repair until may 2009.

The pressure was indeed high enough to theoretically cool. The system had been recharged - supposedly - by Rosenthal Chevrolet in Arlington VA - they have idiots in the mechanics bays - the dealer mechanic did not evacuate the system so it had a significant amount of air in it. This was our theory anyway. Which proved to be true. Using a big shop air line and an air powered evac pump we pulled a vacuum to 28 lbs negative and held it 10 minutes. Then re-charged 2 pounds freon and it has been good to go ever since. Had i known when you and i originally corresponded that the dealer shop could be so lazy i would have gone back up there and stood on them until it was fixed at no further expense to me - as it is I had to put another 80$ into the evac and charge. So I am going to take a pass on your answer and offer the above story for your enlightenment.

Expert:  Dave Nova replied 7 years ago.
Thanks for the update.