72 AC Restoration

[Ed D.]

I am in the process of restoring my AC system. All components are original except the dryer. My Evaporator is leaking and the system needs to be refurbished. The system showed signs of the POA valve or Expansion Valve not working properly, as the Evaporator was freezing up. I plan on replacing all items that are not functioning properly with maintaining originality.
Looking for advice, tips and or directions from prior experience
Thanks
Ed

[Jim T.]

Re: 72 AC Restoration

Ed, The only problem I have had was a easy fix. In the expansion valve inlet is a screen that can be removed for cleaning. Mine in my 1970 was stopped up from the desiccant that came out of the receiver-dehydrator (dryer) and restricted flow through the expansion valve. Replaced the defective receiver-dehydrator and cleaned the desiccant from the system going from the receiver dehydrator outlet line to expansion valve screen. Had the system recharged R12

[Ed D.]

Re: 72 AC Restoration

Jim,
Thanks for the feedback. The only thing that I removed so far is the compressor. I did notice a screen in one of the ports. The screen looked very clean. I have seen tests for the POA valve and the expansion valve, but I have heard that even after testing, these can still be troublesome. I am leaning towards putting 12 back in. Any direction would be appreciated.
Ed

[Patrick H.]

Re: 72 AC Restoration

I disassembled a 76 system, replaced a couple of hoses, and had R-12 reinstalled. If you can get it, I don't see any reason not to use R-12.

If you really wanted, you could have your POA valve and expansion valve rebuilt/restored rather than replacing them. If it were me, I'd lean that direction.

[Ed D.]

Re: 72 AC Restoration

Patrick, thanks for the reply. I was wondering if anyone rebuilt their AC units. I was leaning toward getting the POA valve rebuilt, but in speaking with some members that had experience with rebuilders, they were disappointed. The POA was used from 67 to 72 as I could remember and were troublesome. I plan on doing a check on it when we get it removed. The expansion valve I believe will be less of an issue in checking its performance and or buying a new one or rebuilding it. Have you had any direct experience with rebuilding a POA valve and if yes who would you recommend for the rebuild
Thanks
Ed

[Patrick H.]

Re: 72 AC Restoration

Original Air does rebuilds/restorations.

https://originalair.com/restoration-gm

Old Air Products sells new replacement parts:

https://www.oldairproducts.com/products?car=47-1194-1972on

According to Google, Jeff also works on AC parts:

http://www.broachbuster.com/id49.htm

Let me know what you find out, as I really need to get Dad's AC system on his 72 up and running also.

Patrick

[Harry S.]

Re: 72 AC Restoration

Ed, contact Domenic Tallarita (51287) about rebuilding the compressor. He did mine and several others and the are like new in operation and appearance. He does more than the seals. He take them completely apart and inspect every internal component. Then fixes or replace as needed.

If you contact Jeff about your expansion valve let us know if he rebuilds them. I have my original that is jammed closed and I'd like to get it fixed.

[Ed D.]

Re: 72 AC Restoration

Thanks Harry, compressor is in transport to Dom. I will do more research on the expansion, and POA and get back to you Patrick, with my findings. It is amazing, on a system that is not real complicated, how much mystery is involved.
Ed

[Ed D.]

Re: 72 AC Restoration

In the past 3 weeks I finished the restoration of the AC system on my 72 Corvette. I know there was some interest in how this project went. Here is a summery of the project.
The system had the original component an refrigeration system. The reason for the restoration was due to the evaporator leaking. When dismantling, all components were removed and tested, The only unit that was not removed was the condenser.
The compressor was sent to Dom Tellarita, for a total rebuild and restoration (great communications and workmanship). A new evaporator was purchased at Original Air, as you can not repair them. It was installed without and issues. The POA valve was tested and was bad. A tested NOS valve was purchased from, pacecarjef. Original Air tested and refurbished the expansion valve. A new dryer was installed. All components were installed with R 12 and work and look as good as when the car was new. Hope this was helpful
Ed

[Mark E.]

Re: 72 AC Restoration

Thanks for sharing how this turned out, Ed. Very helpful.

How are the POA and expansion valves tested on a non-working system, or if removed? Can I or a local AC shop do this?

The AC on my '70 worked before put into storage for 20+ years ago. So I'm wondering if/how the POA and expansion valves can be checked before evacuating and recharging. (Hoses, dryer, compressor are being replaced/rebuilt.)

[Harry S.]

Re: 72 AC Restoration

Ed, congrats on the cool air.......

Expansion valve. At room temperature you can blow through it. Put it in the freezer for 1/2 hour and it should close and you will not be able to blow through it. As it warms it will open and again you can blow through it. That is how I tested mine.

[Larry M.]

Re: 72 AC Restoration

Mark:

A very nice POA valve testing procedure was developed on the auto ac forum. I should have the procedure or a link. Fairly easy to do, but you need to buy/make up adapter fitting to fit the POA inlet end to a conventional R12 hose. Also an adapter to go from shop air to R12 hose fitting I have a set a friend made for me that I could loan you if needed. Shop air at 75 psig is used to test.

The POA can also be reset for R134a service. I have another procedure for that. Again, it came from the auto ac forum.

The TXV valve test procedure I have comes from AutoZone Technical library. You use an ice bath and a hair dryer to test flow thru TXV at different temperatures. Also need adapter fittings for both the inlet side and outlet side to TXV to R12 hose. I do not have these. You also make a small drilled orifice to restrict air flow for the test. I will provide a link for this test, but it will take me a few minutes to add it after I post this. So wait for it to appear. The AZ procedure contains both an on-car test and an off-car test. Use off-car one.

I HIGHLY recommend these tests before installing the POA and TXV valves in your system.

Larry

EDIT: Added AZ TXV test procedure link: https://www.autozone.com/repairinfo/...&subtitle=test

EDIT2: The best I can do on the POA procedures is to scan my copies and then send them as an email attachment or send as a hard copy with the adapters/fittings. Autoacforum has revised their database a few years ago and much of the older stuff for our cars is now gone or unavailable to me.

[Mark E.]

Re: 72 AC Restoration

Thanks for the useful information, Larry. I appreciate it.

I'll send a PM with my email address. But in the interest of sharing this with others on the forum, can you post the POA document in this thread? After scanning as a PDF, use the "Insert Image" widget in the menu above your post to insert the entire document. It says it only supports jpg, jpeg, png, gif file types, but I've successfully inserted PDF files this way.

Maybe the administrator can chime in.

[Ed D.]

Re: 72 AC Restoration

Mark,
I had Original Air test both the expansion valve and the POA. I tried testing both myself but was unsure of the results. It was not worth assembling a questionable part and then have to disassemble, especially with the cost of r 12 and how tight it is to get at. The POA valve needs to be cut open to repair, which can ruin the appearance.
Ed

[Larry M.]

Re: 72 AC Restoration

Thanks for the useful information, Larry. I appreciate it.

I'll send a PM with my email address. But in the interest of sharing this with others on the forum, can you post the POA document in this thread? After scanning as a PDF, use the "Insert Image" widget in the menu above your post to insert the entire document. It says it only supports jpg, jpeg, png, gif file types, but I've successfully inserted PDF files this way.

Maybe the administrator can chime in.

Mark:

I will scan the POA valve test procedure and send to you via email as an attachment. I will not scan and send the POA adjustment procedure unless you advise. I will do this in the next few days, as I am simply worn out right now from my volunteer construction work at the church. No ac and ambient temps around 95 F with plenty of sun..........combined with my advancing age.

The AutoZone TXV test procedure is linked in my earlier post and you should be able to view and print it for yourself. Let me know if issues. You can also get directly from Auto Zone Tech Library. It is titled A/C Expansion Valve Testing

If POA connectors/adapters are needed let me know. They are not difficult to make, but do require a bit of time to find and buy the proper connectors and then join them together. But if you do, you will always have set to use and lend out to friends.

Larry