A/C experts? please advise

[John P.]

Hi folks,

My understanding of the ins and outs of my 65 convertible 327/350 with factory A/C has grown significantly due to the input of those on this forum-a hearty thanks to all for making this possible.

Despite that, my general understanding of my factory air system is rudimentary at best. So I am trying to see where to go with my question:

Basically my system might be original, or at least serviced with appropriate parts replaced many years ago. Since my ownership of 20 years, a rebuilt compressor from LIC was installed, as well as some new green gaskets, about 10 years ago., or more. It was converted tp R-134 before I obtained it.

I run the system regularly, and always have. When I take it in for recharge, I am told that there are no obvious leaks. It cools reasonably well for a few weeks or months, then gradually declines in cooling. Ive have never measured the temp at the ducts, but seems reasonably cool initially.

Should I expect more from this system? is an annual or biannual recharge inevitable to get cooling to usable levels? The hoses seem to be standard A/C hoses, in good repair.

Should I ask to replace hoses and gaskets just to see if improvement in lasting results can be obtained? What is the most likely problem in the scenario I have described?

[Bill M.]

Re: A/C experts? please advise

John I had my 67 AC modernized buy a corvette shop. A small aluminum compressor and new crimped hoses because I was adding R 12 every 3 mos. When joe was doing the instal he discovered that my evaporator had a pin hole leak in it and was probably leaking for years.

[Mike M.]

Re: A/C experts? please advise

condensor leaks more common than evaporator leaks but they too can deteriorate. i'd first replace the condenser(easy job exposed in front of radiator. if still leaks off r-12, then replacing the evaporator a much more difficult task. mike

[Harry S.]

Re: A/C experts? please advise

John, I tend to agree with Bill. If it's cooling at 20 degrees below ambient for about a month than starts to get warmer it does sound like a slow leak. You can add dye to the system, then check for traces of it after running the system. It's more difficult to see if it's the evaporator. Hopefully it a fitting or component that is more easily accessible.

I'm running R-12 in my 63 and it has not been charged in 5 years. Therefore, I would not expect an R-134 system to need a charge if it's sealed properly.

[Larry M.]

Re: A/C experts? please advise

Invest in a good electronic leak detector and find the leaks rather than replacing parts. You should be able to get a year or better before needing a can of refrigerant due to minor slow leaks.

Leaks can be:
1. Evaporator
2 Condenser
3. Compressor front seal


4. Old R12 type hoses can leak R134a thru the hose walls due to R134a gas molecules being smaller in size
5. O-ring leaks at the various fittings and joints
6. Possible leak from STV valve itself at the connections and adjustment points.

Items 1-3 and maybe 4 and 6 require an electronic tester to find. Items 4-6 can possibly be found from application of leak-test solution or soap solution.

I can go thru each item with you and how to test...........but you need a tester and some time. All leaks can be found.

My own tester is an Inficon TEK-MATE............reasonable cost and dead-on reliable.

Larry

EDIT: Your factory system should be able to produce 38-42 F at the cabin ducts. Measure it.

[Harry S.]

Re: A/C experts? please advise

Mine was blowing warmer air last year. I bought this tester:

IMG_2549.JPG

I did not have a leak. The problem was the hot water shut-off valve.
It was stuck partially open and letting hot water into the heater core.
Found that with an IR gun. A 15 minute fix with a $100.00 part.

[Arland D.]

Re: A/C experts? please advise

John,

As to 'Should I expect more from this system?' yes. Granted convertibles can be more challenging to cool but my automatic 67 coupe with all factory A/C components and R12 produced more than enough really cold air during 100+ degree temperatures even in very humid conditions.

[John P.]

Re: A/C experts? please advise

helpful info

My car came with a valve installed in each heater hose to and from the heater core. Should these stay closed or open? I realize i need them open in cold weather for heat to be available. I honestly am not sure if the original hot water shut off valve is at all functional, but then that should not cause a gradual lack of cooling, should it?

[Harry S.]

Re: A/C experts? please advise

helpful info

My car came with a valve installed in each heater hose to and from the heater core. Should these stay closed or open? I realize i need them open in cold weather for heat to be available. I honestly am not sure if the original hot water shut off valve is at all functional, but then that should not cause a gradual lack of cooling, should it?

What you describe does not sound like the factory installation. On a A/C C60 car, there should be one hot water shut-off valve on the hose sending water into the heater core. The valve on a C2 is designed to always be closed. Meaning, no hot water into the heater core. The hot water shut-off valve works on vacuum off the back of the carb. The vacuum hose goes from the carb to a switch mounted on top of the under dash heater box then to the valve. When you pull the lever for heat, the switch is opened and allows vacuum to the shut-off valve to open. You get heat in the winter this way or warm the A/C air if it is too cold.

From what you have, keep them closed.

[Edward J.]

Re: A/C experts? please advise

John, A/C leaks are the worst. Sometimes you get lucky and can see and hear the leak, but most of the time the leaks are so small even electronic leak detectors have a hard time unless you pass the wand right over the leak, my first thing I do is a visual inspection, since the system is filled with oil, over the years trace amount of oil will gather at the area of the leak and dust collects on the oil residue. Look at the hood for signs of compressor gas seals leaking, you will see oil spots on upper hood black out, other areas are lower outer parts old the front condenser for oil oil stains, The worst area to locate a leak is the evaporator core, but sometimes the blower resistor in on the can be removed and you can take a bright light and peak in to see if you can spot oily areas down low.(that is generally the area they leak). Good luck.

[William F.]

Re: A/C experts? please advise

1. I thought there is normally a small amount of oil leakage from front of compressor and can see very small amount of oil on undersurface of hood. That's a reason many buy and install the compressor shield that one of our members invented..
2.Concerning adding dye for leak detection. Chevy shop manuals say don't use dye since it can clog the system. I used some once and suspect it caused a problem with POA valve. What do others think?

[William F.]

Re: A/C experts? please advise

One other related question: Should the "pipe" that runs from firewall to POA valve (on a '67) have its entire length covered in the black insulation material or just cover the capillary tube where it contacts this pipe and leave part of pipe back to firewall bare ??
Thanks

[Edward J.]

[Robert W.]

Re: A/C experts? please advise

John,

I, like you, bought a car (327/350HP) with AC (roadster) that had been converted to r134. Next weekend, I'll be switching it back to r12. I literally got my EPA 609 certification so I could buy a used 30# tank! I think r134 can work fine, but at best in a C2, it's weak. I have r134 in a 1966 Mustang with a Sanden compressor and it works pretty well there. It's definitely a mess flushing the system and switching back to mineral oil and r12, I'll let you know in a ~month if it was all worth it

[Greg H.]

Re: A/C experts? please advise

Hi John,
You MUST stop / eliminate all of the hot coolant from entering your heater core that is concealed inside the air supply plenum that is inside your car. No amount of Freon can cool a hot heater core!

The plenum is configured so that the cool air and the heater core share some of the same internal chambers and if the heater core is heated to 180 degrees your system will not cool.IMG_0799.jpgIMG_0793.jpg