A/C System Repair

[Clark K.]

I have had my '65 A/C Coupe in the shop for the last week. The dang thing kept losing Freon and since I want everything on my car to work properly, this became a big issue with me. I had paid big bucks to have my car's A/C system restored last winter in preparation for Flight judging. After getting the car back from the restoration shop, I expected the A/C to work properly. Well, it didn't. It just didn't cool for long. With that shop charging me $80 per pound for Freon, it adds up quickly if your system loses 2 to 3 pounds of Freon every few months.

Well, after getting the car home from the San Diego National Convention, the A/C no longer cooled the interior. I took it back to the shop that did the A/C restoration work. After keeping my car for a week, they told me today that they think that they found the leak. It was in the two original Schraeder valves in the compressor manifold. These valves were leaking. So, any of you out there with leaking A/C systems, you may wish to check those original Schraeder valves.

The shop's owner told me that the repro correct hoses and hose clamps for the refrigerant are prone to leak and did so when new. He said that it was common in the 60s to have to add one or two pounds of Freon every summer season. What do you guys who owned A/C Sting Rays back in the day have to say about this?
-Clark

[Tom L.]

Re: A/C System Repair

When compressors sit the shaft seal can "dry" out as the oil wicks away. This is caused by lack of use. Can't speak specifically about vettes but adding some gas each sprong was not uncommon. The reason it sdidn't leak out was the compressor was being used and the seal remaines coated with oil until it sat for the winter, after that the cycle began again.

Your leak seems to be a challange for shop you're using, not uncommon. To avoid finding that the leak is still there after having it re-charged at $80/lb. perhaps ask the shop to take a different approach. Pull a deep vacuum, record the vacuum it is at and let it sit for a while and re-check it. The vacuum should still be the same. Air will leak in as easily as gas will leak out. You might save some money if the Schaeder valves are not the culprit (?). Good luck!!

[Larry M.]

Re: A/C System Repair

As you stated in your initial post, the Schrader valves can leak.....BUT each valve should have a cap on it with an inner o-ring seal that will prevent leakage when the cap is installed tightly on the connection! Check for the o-rings.

If you haven't already done so, have this shop (or another shop) go over your system with an electronic refrigerant leak tester. With R12 costs what they are, this tester pays for itself quickly, and I recommend that folks with AC cars get one (borrow, rent, or buy). I recommend the TEK-MATE as it is very good and also relatively low cost ($150). These testers will locate even the slightest leak, and can also easily check the evaporator coil and compressor seal. A soap test cannot really do this.

Back in the day, these systems usually leaked a can of R12 every year from someplace(s) in the system. New (non barrier) AC hoses should be okay for R12 but are not okay for R134a. Do you have the barrier hoses?? With continued operation, even the non barrier hoses will get coated inside with refrigerant oil which will slow down or stop any migration refrigerant loss through the rubber wall.

I am not certain that your shop is the best one for AC service. If you are not satisfied, find another.

Larry

[Randy S.]

Re: A/C System Repair

Clark,

"The shop's owner told me that the repro correct hoses and hose clamps for the refrigerant are prone to leak"

When I did my 66 a few years ago my only choice was barrier hoses for use with 134a. Barrier hoses have a plastic liner built in to prevent leakage of 134a, a smaller molecule than R12. Long Island Corvette then came out with repro hoses with the correct lettering on them and I do not know it they use barrier hoses or standard non barrier.

Check to see who the supplier of your repro hoses is and if they are barrier style they are not likely leaking thru the hose itself. Most AC shops put a dye in the system to check for leaks so I would have them use the special light and glasses and look for the leak.

Randy

[William C.]

Re: A/C System Repair

A small leak over a year, enough for a small can or R-12 to fill, MAYBE (more likely 2-3 years) , but 1-2 lbs? Find an AC shop that has actually been in business for 25+ years. Your shop is incompetent!

[Clark K.]

Re: A/C System Repair

New (non barrier) AC hoses should be okay for R12 but are not okay for R134a. Do you have the barrier hoses?? With continued operation, even the non barrier hoses will get coated inside with refrigerant oil which will slow down or stop any migration refrigerant loss through the rubber wall. Larry

Since my A/C system was under warranty, the shop did all the diagnostic checks (leaks, etc.) and refrigerant addition on their own. I only paid for the labor to repair the two Schrader valves ($161).

The hoses and clamps that are on the car are those I bought from Long Island Corvette last winter. I wanted them since they incur no originality point deductions during Flight-judging. Whether they are barrier-type, I cannot tell you. I am still using Freon (R-12).
-Clark

[Clark K.]

Re: A/C System Repair

The car is back in my garage as of Tuesday afternoon. When I got home, I put an A/C thermometer in the center vent and after a minute, the temperature read 51 degrees (F). The ambient temperature was about 95 degrees (F). Is this a nominal vent temperature for the conditions?
-Clark

[William F.]

Re: A/C System Repair

No, it's not cooling down enough, actually doing very little. Check specs in Chassis manual-should be around 44-42 IF measured in righ side vent, fan on high, lower AC knob pushed all the way in to get only recirculated air, and at about 2000rpm. Something very common that no one else has mentioned is possibility of heater valve not closing completely. Most DON'T. Many put a cutoff valve in at least the inlet heater hose. Check this possibility right now.

[Clark K.]

Re: A/C System Repair

Check specs in Chassis manual-should be around 44-42 IF measured in right-side vent, fan on high, lower AC knob pushed all the way in to get only recirculated air, and at about 2000rpm. Something very common that no one else has mentioned is possibility of heater valve not closing completely. Most DON'T. Many put a cutoff valve in at least the inlet heater hose. Check this possibility right now.

After receiving William Ford's reply, I did the checks yesterday that he encouraged. The ambient air temp was 88 degrees (F), the idle was brought up to 2,000 rpm, the A/C fan speed was set on high, the thermometer was placed in the right-side vent, and the lower A/C knob was pushed in fully. The heater valve was closed. After about a minute: 41 degrees (F).

So, I guess I should be happy. I have been told that a 40 degree differential between outlet (vent) temp and ambient (outside air) temp is all that can be expected. But, with the L76 (solid-lifter cam, high compression) engine, the coolant temp shoots up quite quickly sitting still! The temperature gauge shot up to over (what I call) "the 3/4 mark" within two minutes, sitting still with the idle at 2,000 rpm. These L76-A/C cars must be moving on the highway to use the A/C.

I am still unsatisfied with the stock cooling. I want stiff nipples! The highest A/C fan speed is just not enough. I need a "fourth speed"! The cabin cooling is just not sufficient for Texas summer heat. I am thinking that when the carpets are replaced, some sort of modern insulation should be used under the carpet. Also, electric fan(s) are needed for city driving during hot weather with the A/C engaged.
-Clark

[Ken A.]

Re: A/C System Repair

36-38 degrees was GM's recommendation. You have a refrigeration system, not a typical A/C system. The only thing else you didn't do was have a huge fan blowing air over the radiator/evaporator to simulate real driving conditions. Two things that will help-make sure the evaporator drains are intact and not rotted off and buy more corkwrap & wrap the cold pipe all the way from the compressor to the evaporator.

[Don H.]

Re: A/C System Repair

Clark, I have had three mid-year air coupes over the years putting many miles on them and still have a 65. I had this system working well for many years and recently went through a three year struggle to get it to hold R-12 (finnally fixed). A few observations: They will go down to around 40 degrees when working well. They will need a little R-12 added every 1-3 years. They will not cool well with 134, keep using R-12. Disconnect and plug the vacuum line to the coolant shut off valve in the summer, that way you are sure there is no leakage. Good luck, Don H.