Any HVAC experts around?

[VetteMed]

The AC system is giving me fits. I've got a new compressor/condensor/evaporator/accumulator/orifice tube. I added 3 oz of mineral oil to the evap, 2.5 to the accumulator, 1 to the condenser, and around 3 to the compressor. I evacuated the system down to 29.9mm Hg, let sit overnight, then evac'd again, then added 36 oz of R12 (the factory spec).

Cooling is nonexistent, the system cycles very rapidly, every 3-4 seconds, the low side gets cold but the evap fins do not get cold and therefore the air does not get cold. I disassembled the system today and found over 8 oz of oil in the evaporator, hardly anything in the other components. WTF is going on?? The Ac control panel indicated code 09, low freon, so against my better judgement I added another 12 oz, which did nothing to help the situation.

[lbszr]

Originally Posted by VetteMed

The AC system is giving me fits. I've got a new compressor/condensor/evaporator/accumulator/orifice tube. I added 3 oz of mineral oil to the evap, 2.5 to the accumulator, 1 to the condenser, and around 3 to the compressor. I evacuated the system down to 29.9mm Hg, let sit overnight, then evac'd again, then added 36 oz of R12 (the factory spec).

Cooling is nonexistent, the system cycles very rapidly, every 3-4 seconds, the low side gets cold but the evap fins do not get cold and therefore the air does not get cold. I disassembled the system today and found over 8 oz of oil in the evaporator, hardly anything in the other components. WTF is going on?? The Ac control panel indicated code 09, low freon, so against my better judgement I added another 12 oz, which did nothing to help the situation.

Not claiming to be an expert. But it sounds low, if it doesn't have some other part failure. Do you have guages connected to low and high? What are the pressures?

Mine was pretty picky about having the correct amount of freon in it. It had too much and wouldn't cycle.

[limey]

Cycle on and off is the cars way to bleed of air pressure, that's whats happening. The freon isn;t circling the whole system it would seem, put a jumper wire on the low side and high side and the clutch should kick in and stay on. That will then get the freon to go round the entire system.

[VetteMed]

Well, I think I found the problem after some extensive input on a couple of other forums. The evaporator core appears to have an internal blockage.

[cvette98pacecar]

AI am an expert on this matter. There is a metering device that needs to be cleaned. On the inlet fitting of the evaporator you are going to have a screen that needs to be cleaned. Dip in Virgina 10 cleaning solution over night than soak it in refrigerant oil and dry it off with a clean lint free rag. If you have access to Nitrogen when you have the fitting apart blow nitrogen threw the evaporator backwards. While a vacuum pump will remove non-condensible it will not move moisture. If you have any other HVAC problems send me a PM. Here is a link to the Granger part number.

http://www.grainger.com/Grainger/VIR...NJ8?Pid=search

[VetteMed]

Actually with the help of someone on the other forum, who cut open his spare evaporator to compare to my cut open evaporator, it was determined that my evaporator was assembled without a critical part.

replace the stupid asterisks with corvette forum.

http://forums.*************.com/c4-t...ith-oil-3.html

[HAWAIIZR-1]

Andrew,

I hope you don't mind if I ask a question here for HVAC experts?

My A/C runs fine at idle but when driving it starts to stumble only with the A/C on. If I turn it off the car drives fine and turn it back on the and the cars starts to hesistate and stumble? If idling you can see the clutch engage and disengage and cold air is present like normal. Craziest thing to me and probably nothing to do with the A/C system?

Thanks!

Craig

[cvette98pacecar]

Originally Posted by HAWAIIZR-1

Andrew,

I hope you don't mind if I ask a question here for HVAC experts?

My A/C runs fine at idle but when driving it starts to stumble only with the A/C on. If I turn it off the car drives fine and turn it back on the and the cars starts to hesistate and stumble? If idling you can see the clutch engage and disengage and cold air is present like normal. Craziest thing to me and probably nothing to do with the A/C system?

Thanks!

Craig

Sounds like you have non-condensible in system. As you raise the RPM of the motor the compressors pumping ratio goes up (you move more refrigerant) so if you have non-condensible (which are usually trapped in the Condenser) the refrigerant is not sub-cooled and raises the pressure. At this point the compressor cant no longer push and refrigerant and causes the AC clutch to bind.
Now if you have not had any type of AC work done in the last couple of years this is highly unlikely.
A good was to check this is take a reading of the temperature of the liquid line (line that goes from the condenser to the evaporator) at idle and them after driving. The liquid line should be colder after driving.

[HAWAIIZR-1]

Originally Posted by cvette98pacecar

Sounds like you have non-condensible in system. As you raise the RPM of the motor the compressors pumping ratio goes up (you move more refrigerant) so if you have non-condensible (which are usually trapped in the Condenser) the refrigerant is not sub-cooled and raises the pressure. At this point the compressor cant no longer push and refrigerant and causes the AC clutch to bind.
Now if you have not had any type of AC work done in the last couple of years this is highly unlikely.
A good was to check this is take a reading of the temperature of the liquid line (line that goes from the condenser to the evaporator) at idle and them after driving. The liquid line should be colder after driving.

Thank you very much for the info and possible cause. There was some work done a few days before the vehicle was shippped. My A/C was not cold and seemed to have lost refrigerant while it was down for motor rebuild. The A/C technician thought there might be a leak and recharged the system with dye and two days later it was shipped. That was all he could do for me and told me to get a black light and try to check for leaks later upon arrive in Japan. During the time prior to vehicle being shipped I did not have the issue of the surging with A/C on. It was not until two months later that the vehicle arrived in Japan and then this issue. The battery was dead and was recharged, then driven from the port to my home (20 min drive) no issue noted. The next day it was driven an hour each way to the Navy base to check emissions/exhaust system and both way during that trip it was experienced so it could not be used. It has been parked since waiting on all my emissions parts. Thanks again.