Converting to R134a on my '63

[Michael Forte]

Hi All,

I wanted to share my experience converting my factory air system to 134a refrigerant, hoping it will save you time and money.  After I changed the parts, I got my system charged professionally and it works amazingly well, blowing ice cold at the vents.  Here's what I did:

I started with a call to Old Air Products (oldairproducts.com) from Texas.  I'm usually the guy who researches everything alone and then buys the parts online without ever interfacing with a human, but A/C is one of the only parts of a car that is (was) a mystery for me so I decided to call on the experts.   I couldn't find complete information on their website, so the call was essential.  They were technically competent and no pressure to sell.  I told them I had a non-working factory air and wanted to convert from R12 (I assume that's what was in there) to R134a.  The compressor appeared to be original and its internal condition unknown, so a remanufactured one was recommended to avoid problems.  I chose an A6 over a modern replacement version (Pro6TEN) since I preferred the stock appearance.  Here's the parts list and Old Air Products Part Numbers:

• Remanufactured A6 compressor - 21-3215-10 *
• New high pressure hose - 95-6507
• New suction hose - 95-6508
• New receiver/dryer -21-4215A *
• STV Upgrade kit - 50-2500P
• New expansion valve - 25-0054
• 90 degree 134a adapter (low side) - 91-954M
• 90 degree 134a adapter (high side) - 91-953M

*Note that the compressor had a smaller pulley than original and the receiver dryer was smaller than original.  See the "important notes" section below for details and talk to your supplier about options.

I encourage you to call Old Air Products (or your preferred supplier) and talk to them about what you want to accomplish.

Once the new parts arrived, I started by removing the old hoses, expansion valve, hard line, receiver/dryer, and compressor.  I flushed out the condenser with AC Pro Power Clean and Flush that I bought at the auto parts store.  Also flushed out the hard line from the expansion valve to the dryer (after removing it from the car).  I did not flush the evaporator.

After everything was clean and blown out with compressed air, I started assembly.  The STV upgrade kit comes with everything you need to change the system to cycling clutch type, so I followed the instructions and everything went well. I made sure the compressor had the recommended amount of PAG 150 oil (10 oz), and assembled all the hoses and parts.  The kit contained enough new O-rings to do the conversion 3 times, haha, so don't worry if you drop one into the frame rail.

After everything was back together, I went to Autozone and borrowed a vacuum pump and a set of A/C gauges.  Following the instructions, I pulled a vacuum and let it sit overnight.  No leaks!  Ready for charging!

I wasn't about to charge it myself so I found a reputable local shop and let them do their thing.  I mentioned to them that the service manual called for 4lbs (64oz) of R12 for a completely discharged system (as mine was).  I also gave him a conversion factor for R134a I found on the internet which said I'd need 53oz of 134a, because apparently less 134a is needed than R12.  It turns out that the system stopped accepting refrigerant after 34 oz was delivered, and the system now functions perfectly.  I can't explain the shop manuals 4lb requirement nor can I explain the conversion factor an internet "expert" suggested.  34 oz of R134a works so I'm sticking with that!

I took a few measurements to see how the A/C would perform on a hot day.  With an outside temp of 88 degrees at around 2:30 with full afternoon sun, I measured 35 degrees at the driver side vent in idle and 32 at the center vent.  At cruise speed and at higher rpm, vent temps are much lower - I measured 28 at the drivers vent and 24 degrees at the center!  Outside surface temps of the car were over 100 but inside was comfortable.

I've driven the car on a couple of 90 degree days and have been pleasantly surprised that old school A/C in a convertible can perform so well.

A couple of important notes:

• The A6 compressor I bought came with a 5" pulley (measured overall diameter).  The original compressor had a 6" pulley.  I could have sent the compressor back for an exchange, but the tools for changing the pulleys can be borrowed from Autozone so I did the swap myself.  Fortunately, my original pulley was in great condition.  Make sure you specify when ordering.
• If you're going for concours quality (I'm not), the paint on the reman compressor is not correct.
• The R134a fittings do not look like the originals, but you might get black caps or paint them to make them less visible.
• The hoses from Old Air Products look like the originals except for writing on them (manufacturer and part number and such).  You might be able to remove the writing with a solvent.  It's not obnoxious, but not concours correct. They're manufactured with modern materials and compatible with R134a refrigerant.
• The receiver/dryer came unpainted raw aluminum and is smaller than original, factory brackets will need modification.  Stock ones are hard to get because the cores are rare.  You could send your original to be rebuilt if originality is a concern.
• The expansion valve looks original but seems to have more coil length than original. The coil is copper so again, some black paint would help hide it.
• The STV conversion basically removes the internals of the valve and closes off the vacuum actuator functionality.  The valve will appear stock after modification.  There is a small relay that needs installed, you'll have to hide it if you want a factory appearance. 

I hope this post helps you.  Sorry I didn't take progress photos - I hadn't thought of blogging the experience until I was done.  I added a few "after" photos below that give you an idea of what the parts look like. 

Total cost was $675 for all the parts, and $175 for the refrigerant and labor to charge the system.

If you have any questions or need related info, just ask.

-Mike

Photo 1: Receiver/Dryer in raw aluminum.  Note that the replacement is a shorter "bottle" than original.

Photo 2: This is the remanufactured A6 compressor and the R134a fittings.

Photo 3: Another view of the fittings.  I ordered 90 degree adapters because of the size of the gauge and charging system connectors.  I didn't think straight fittings would allow those connectors to fit.

Also note the writing on the low pressure hose.

Photo 4: The modified STV (left) looks original from the outside, as does the expansion valve.  The silver relay on the right is the compressor cycling relay.  When the surface temp of the evaporator outlet gets too cold, it shuts off the compressor.  Seems to activate somewhere between 15 and 20 degrees.

[Michael Forte]

My understanding is that R134a requires different operating pressure than R12 to work correctly. The STV is a pressure regulator that has a spring inside that is calibrated for R12 pressures. Perhaps a different spring is available for 134a, I don't know. The kit I used basically renders the STV non-functional and uses the relay and compressor cycling to regulate pressure.

Before going into that though, check to make sure your vacuum system is working properly. The STV, heater valve, and temperature blend doors use vacuum. You might have the wrong flap open or having the heat blending with the a/c warming it up. A quick check would be to touch the STV while the a/c is on. If your charge and pressures are correct, it will be ice cold. If it is and your vents are warm, check your vacuum system and a/c controls.

[Jason Edge]

Perfect. I'll put it into the next Newsletter! 

[Michael Forte]

I just updated the blog post with pics and temperature measurements.  Let me know if you have questions.

[Michael Forte]

I didn't check the outside temp when I measured it but I remember it was hot enough to need air conditioning, probably mid 70's.  I'll test it this weekend (forecast is 87) and post the inside and outside temps in the blog. Thanks!

[Michael Forte]

Thanks Jason! Much appreciated! I'll try to get some pics over the weekend and add them to the post.

Regards,
Mike

[Jason Edge]

ps. I went ahead and put an entry on the Help page pointing to this article. If we do an newsletter article with final pictures we can point to it. thanks! Jason.

[Jason Edge]

Hi Michael, I have been busy with house projects this week and have been chomping at the bit to reply to your excellent write-up!  This would make an excellent Tech Tips article for a future newsletter, and we can then crop it out and post as a separate article on the Help Page. I understand you did not take pictures through the process... which is fine. But, it would be great to take pictures of your final results and include. I especially appreciate the fact you took the time to point out how to make it look more factory original several times!  If you were on eBay I would give you one of those A++++++ Ratings! Great article! I appreciate the detail and the fact it follows the 4 C's of writing - Clear, Concise, Correct, Complete.

[Michael Forte]

Thanks for the positive comments on my first blog attempt!  I updated it to answer the questions I've been asked so far. 

For Robert, I revised the blog to put a description of the items and the cost in there.  If you want show quality originality, I'd repaint the compressor and make sure to either get an original-type receiver/dryer or have your original rebuilt.  You're luck to be able to go and talk face to face to those guys.  Good luck.

Thanks Clovis for positive comment.  I hear '64 climate control is challenging, but don't fear it.  Go for it!

Thanks Tony and Ginny for positive comments.  After doing the swap, I'd have no fear of doing it again.  If you have decent mechanical skills and take your time, it's a pretty easy job.

Good luck with your projects!

Regards,

-Mike

[Robert Alan Shannon]

Thank you Mark for this great info. This is probably in my future with my 63. My A/C  worked fine last  time I used it but that was way back ,bout 15 yrs ago. Did all the new parts look original or acceptably close. I'm driving distance to that business,in southern OK.. Curious  about  the cost  as well.