C2 Air Conditioning Issues -One More Try

[Joseph S.]

Have been working on the factory AC system in my '66 for a bit of time now. With the help of a number of people on the forum have got the system rebuilt and leak free. However after a few times having the STV rebuilt I am still not able to get the suction pressure down below 75-80 psi (high pressure is about 80-90psi on cool day).

Obviously with that high a suction pressure and charging with small cans (134a) I cannot get much refrigerant into the system.
I adjust the STV spring all the way out (CCW) with little change. My valve seems to only have 2 or three turns from stop to stop with a lot of spring pressure friction, not sure if this is normal.

I am assuming the issue is STV, I would open up the valve maybe find a NOS piston and diaphragm to install, but assume I (with no experience rebuilding them) would not be able to do better than the guys at Original Air that worked on it before.

Looking for someone to rework the STV- I'm assuming a there is an internal issue with the piston. Joe

[Tom L.]

Re: C2 Air Conditioning Issues -One More Try

I hate to even bring it up but you are certain that the clutch is engaged and the compressor is turning, right?

Gauges are on the ports on the compressor?

That being said, it does sound like the compressor is not pumping. Since there are 2 sets of valves and you see minimal difference in pressure I'd think that valves were not the problem. The reason is that if 1/2 the valves were working you'd see a greater difference in pressure from the discharge and suction sides of the compressor.

May be something catastrophic internally given the pressures. Once you've confirmed that the compressor is turning it may be time for a teardown. Others will chime in I'm sure.

[Larry M.]

Re: C2 Air Conditioning Issues -One More Try

Joe:

Unfortunately I can't help with rebuilding the STV. You may have to go to an STV bypass with a temperature (low) cut-out. At least you will have AC for the summer.

I can help with the charging from cans: Although I do not like to recommend it to most folks due to potential downsides, you can charge the system with all liquid from cans before even starting the engine and compressor. It takes a bit of knowledge and a little time to make sure all the liquid gets out of the compressor before it is energized..........but it is doable by most folks with some coaching. So let me know if you want to try this.

Originally GM (as well as folks with AC refrigerant recycle machines) do this/have done this. You basically charge all liquid into the compressor discharge (condenser and receiver/drier hold the liquid as normal), let compressor stand for awhile with some warm heat under it (shop light) and then rotate the compressor a few times to help clear it completely of any liquid. I believe GM just used a longer time interval on the production line between charging as a liquid and finally starting the engine and compressor............giving the system time to normalize.

FWIW.

Larry

[Joseph S.]

Re: C2 Air Conditioning Issues -One More Try

Thanks for the input.
Tom, the compressor is engaged, gauges hooked up to the correct ports (only 2 on this car) and compressor was rebuilt by Dominick Vermet. So unless I screwed something up I'm feeling the compressor is doing its job. Actually the compressor is doing some work even with the low (maybe 6oz) refrigerant level in the system since I physically can feel a difference in the temperatures of the suction and discharge pipes on the compressor and the evaporator drain is dripping a few drops of water.

As for charging the system with all liquid. I would like to give it a try before I break the system down again. If there are any more instructions beyond what you have noted in your post, please pass them on. Joe

[Larry M.]

Re: C2 Air Conditioning Issues -One More Try

Joe:

We should talk before doing this..........just so you understand all the steps and sequence.

Larry