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Discussion Starter · #1 ·
Hi everyone. I have a '64 SS that came with factory a/c. It's not working properly. It doesn't blow cold enough air. I'm not trying to compare it to modern day car a/c, but this just isn't working properly. The fan/blower works fine and when you push down the one lever for the a/c, the compressor engages and the engine rpm decreases slightly. I had it to a mechanic who replaced some type of vacuum switch controlling the heat and a/c. He said that the previous owner converted it over to the modern refrigerant and it was full. He seems to think that everything is working properly, but I don't. The air will get slightly cooler but not cold. With winter coming, I certainly don't need the a/c or will even be driving the car much longer. I spoke with the mechanic the other day and told him of my concerns. He is a real decent guy and said to bring it back in the spring and he'll check it some more. I know little to nothing about a/c. I guess there are 3-4 main parts to it. Based on my description, is there something we should be looking at again?? Some thing I can gently pass along to him?? Thank you, Carmine.
 

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it is probably overcharged with too much freon or oil or both.
 

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it is probably overcharged with too much freon or oil or both.
I agree with Hotrodg726 here. The old systems do not need as many ounces of 134 as the R12 they originally required. I have seen it many times where a particular old system required 3 LBS of R12 freon and the person converting it puts 3 LBS of 134 in, NOT going to work/cool properly. Another possible cause I have seen more times than I can count is someone didn't evacuate the system before charging it, NOT going to work/cool properly. There are a few other things that could also be your problem. Take it to someone that is familiar with converting older systems to 134 or you are just wasting your time & money. :anim_25:
 

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Trifive Automotive Electrical Wiring Expert
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It could be several things, such as air or water in the system from being improperly vacuumed down when it was converted, the water control valve not shutting off completely, the thermostat stuck, or a bad expansion valve. I'm pretty sure it uses a expansion valve.
 

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A/C PROBLEM

I agree with the other tri-fiver's in that the R134 is NOT going to be as efficient as the R12 since it runs at higher pressures, which results in HEAT, and, in that regard, less efficiency and not so cold "air" especially at idle! R134 is real "finiky" in that IF you undercharge OR overcharge, it really affects the air quality and temp. of the air discharged thur the air ducts! If you think about it, the system was designed for R12, which, as I mentioned before, runs at lower pressures, which in turn, gives out more colder-type air! I would recommend as one of the other members brought up, is to make SURE you evacuate[vacuum] ALL air and moisture from the system, as well as please replace the receiver/dryer[accumulator] before you vacuum the A/C system and recharge, remembering that, "usually", it takes about 80% of R134, of what the system takes w/R12! Good luck and hope this may help you!:anim_25:
 

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Acardon is on the right track. Further...what refrigerant was the system converted to? The metering device may need to be replaced. If the tech inherited this issue from another tech he may want to recover the existing refrigerant, change the drier if there is one, pull a deep vacuum. Hold 4 hours, purge dry nitrogen, pull another deep vacuum (at least 25 microns), install new refrigerant and check system operation. Yes, I know...a lot of steps. Really a day while doing other work. :anim_25:
 

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Some good comments here.

One of the problems with working on an a/c system when the weather is cool is that it gets more difficult to evacuate the system properly and actually get all the water vapor out. I don't think I'd even attempt it if the temperature is below 70*F.

The amount of refrigerant required with R134 is about 80-85% by weight of the recommended charge of R12.

What kind of metering valve is on a 64 Chevelle? I'm guessing it's probably an expansion valve. They used POA valves late in the 60s but I don't know when they started. An expansion valve is probably more forgiving with the R134.

If it was mine, and it's been converted to R134 rather than some R12 substitute, I'd wait until spring. I'd put gauges on it and diagnose whether it's overcharged/undercharged/whatever. If it's not an obvious overcharge or undercharge, I'd break down all the connections, drain all the oil, replace the drier, put all new O-rings on the connections, flush all the components, evacuate, and recharge with fresh oil. When the temperature is over 70*F or even warmer.

If it was converted to some R12 substitute, I'd scrap that and convert to R134, and do what's in the above.
 

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Discussion Starter · #8 ·
Some good ideas here and much food for thought. With winter approaching, I won't get back to this until late spring/early summer. But, I will have a game plan and idea of what I have to do, what to check. Thank you everyone for your replies, Carmine.
 
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