Can I use an NOS 71 Expansion valve with R134a or do I need to replace with a new one?

kevken1959 · Oct 28, 2024

About to charge the A/C on a low mile 73 I bought. I've pulled the factory expansion valve and the dryer and want to replace with new before I recharge with R134a. I have an NOS expansion valve I could use but will it work with R134a?

Thanks!

Kevin.

MikeGriese · Oct 28, 2024

You need to do more than that to make the switch - extracting oil, replacing o-rings, maybe hoses. The R-134A molecule is smaller than R-12 and can leak out of the older hoses.

Sheriff41 · Oct 28, 2024

If your expansion valve was working before, there is no need to change it. I'd definitely replace the receiver/dryer if it's been open to the air for a while.

kevken1959 · Oct 28, 2024

MikeGriese said:
You need to do more than that to make the switch - extracting oil, replacing o-rings, maybe hoses. The R-134A molecule is smaller than R-12 and can leak out of the older hoses.

Thanks Mike.

kevken1959 · Oct 28, 2024

Sheriff41 said:
If your expansion valve was working before, there is no need to change it. I'd definitely replace the receiver/dryer if it's been open to the air for a while.

Thanks Chuck.

kevken1959 · Oct 28, 2024

I plan to blow some compressed air through the lines, the evaporator, and the condenser. Everything looks good though from what I can tell. Should I suck the oil out of the compressor and replace it with PAG oil if I am going with R134a?

Sheriff41 · Oct 28, 2024

Yes. I'd go with a completely evacuated system and add the correct oil charge when servicing. Don't over do it on the air pressure.

EDIT: Be sure when you evacuate the system you check that it holds vacuum. I usually let it hold for 30 minutes, just to be sure.

Steve McMahan · Oct 28, 2024

Did I miss why the conversion from R12?

Bill Kanode · Oct 29, 2024

kevken1959 said:
About to charge the A/C on a low mile 73 I bought. I've pulled the factory expansion valve and the dryer and want to replace with new before I recharge with R134a. I have an NOS expansion valve I could use but will it work with R134a?

Thanks!

Kevin.

I have been restoring EVERYTHING on my 1971 351C Fastback including the AC system. I bought a new 134a expansion valve, hoses, and everything else associated with the System. I bought a new larger condenser and sent my original compressor to Texas for rebuild with improved O rings so I would have original parts as much as possible especially the large flywheel it uses. My guess is that Ford used the larger AC compressor flywheel to prevent RPM fluctuations when energized as well as the idle solenoid to raise engine speed when the compressor comes on. It would have been cheaper to get a new Communist China made unit or Autozone rebuilt but I wanted the larger flywheel. Thx, Bill ⁷

kevken1959 · Oct 29, 2024

Steve McMahan said:
Did I miss why the conversion from R12?

Good question. It would have been so easy to just put some R12 in it but I just figured it was too expensive and hard to get. It's not too late to go R12. I can install the NOS expansion valve and the new dryer. Suggestions?

kevken1959 · Oct 29, 2024

Bill Kanode said:
I have been restoring EVERYTHING on my 1971 351C Fastback including the AC system. I bought a new 134a expansion valve, hoses, and everything else associated with the System. I bought a new larger condenser and sent my original compressor to Texas for rebuild with improved O rings so I would have original parts as much as possible especially the large flywheel it uses. My guess is that Ford used the larger AC compressor flywheel to prevent RPM fluctuations when energized as well as the idle solenoid to raise engine speed when the compressor comes on. It would have been cheaper to get a new Communist China made unit or Autozone rebuilt but I wanted the larger flywheel. Thx, Bill ⁷

Thanks Bill!

kevken1959 · Oct 29, 2024

Sheriff41 said:
Yes. I'd go with a completely evacuated system and add the correct oil charge when servicing. Don't over do it on the air pressure.

EDIT: Be sure when you evacuate the system you check that it holds vacuum. I usually let it hold for 30 minutes, just to be sure.

Will do Chuck. Thanks!

Steve McMahan · Oct 29, 2024

While some OEM r134 systems cool very well, they were designed from the ground up to do so. Ours is a conversion or a retrofit. So, we’re giving up some capacity for the convenience of available materials in the future.

If it were mine, and I am facing this decision very soon, I would keep the r12. Not because it keeps it original, but it keeps it as a set of components designed to work together. And, r12 wasn’t replaced with r134 because it was a better transfer agent; it was just one that had fewer issues related with o zone related gases. So, since it’s no crime to use it, I say do so.

Others may have other opinions.

kevken1959 · Oct 29, 2024

Steve McMahan said:
While some OEM r134 systems cool very well, they were designed from the ground up to do so. Ours is a conversion or a retrofit. So, we’re giving up some capacity for the convenience of available materials in the future.

If it were mine, and I am facing this decision very soon, I would keep the r12. Not because it keeps it original, but it keeps it as a set of components designed to work together. And, r12 wasn’t replaced with r134 because it was a better transfer agent; it was just one that had fewer issues related with o zone related gases. So, since it’s no crime to use it, I say do so.

Others may have other opinions.

Thanks Steve.

basstrix · Oct 30, 2024

You might try doing some research into "R12 replacement options". There are some approved replacements out there. A friend, in the HVAC business, recommended I look at Hot Shot-2.

Scram mustang · Oct 30, 2024

Maybe this will work? https://www.amazon.com/Generic-Arct...=se&keywords=r-12+freon&qid=1730305232&sr=8-2

Bobby · Oct 30, 2024

MikeGriese said:
You need to do more than that to make the switch - extracting oil, replacing o-rings, maybe hoses. The R-134A molecule is smaller than R-12 and can leak out of the older hoses.

It would also behoove you to replace the dryer and the condenser. Flush out the evaporator and replace the expansion block with a new one. I would also replace the compressor since it would be difficult to extract all the oil for replacement. Either concourse replacement or the newer compressors will work. However, the newer compressors use about half the horsepower to run compared with the older designed compressor.

mrgmhale · Oct 30, 2024

With respect to the earlier mention(s) of needing to change the refrigerant oil if moving to R234, the old R12 compatible refrigerant oil needs to be completely removed. As for the new refrigerant oil, use only a R134 compatible oil. BG has a universal refrigerant oil, and I have heard from one trusted source that it works well. I do trust their products.

https://www.bgprod.com/blog/univers-oil/

https://www.bgprod.com/

kevken1959 · Oct 31, 2024

basstrix said:
You might try doing some research into "R12 replacement options". There are some approved replacements out there. A friend, in the HVAC business, recommended I look at Hot Shot-2.

Thanks!

kevken1959 · Oct 31, 2024

mrgmhale said:
With respect to the earlier mention(s) of needing to change the refrigerant oil if moving to R234, the old R12 compatible refrigerant oil needs to be completely removed. As for the new refrigerant oil, use only a R134 compatible oil. BG has a universal refrigerant oil, and I have heard from one trusted source that it works well. I do trust their products.

https://www.bgprod.com/blog/univers-oil/

https://www.bgprod.com/

Thanks!

Can I use an NOS 71 Expansion valve with R134a or do I need to replace with a new one?

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