Hi,

I changed over to 134a on my 69 Chevelle with factory air but am now working on replacing a number of components and came across in the Year-One catalog that the only expansion valve listed is not for use with 134a and they don't list another model. What is the deal with this?
I thought you could use the original expansion valve from the R12 system. Is there another one that works better or something? Other aftermarket suppliers don't mention this and there is only one part no. listed. I've been having problems and when it was working, it was not real cold. Is this maybe the reason its not real cold and will the original type of expansion valve work? Appreciate any help.

Thanks,

RwS

I don't know why they would say it was not for use with R134a. There shouldn't be any compatibility issues. There are R134a specific valves that operate at a slightly different pressure, but not for any "old" automotive application that I'm aware of.
With that said, I would source the TXV from another source such as NAPA just to avoid any problems.

The key to getting the AC in your 69 to cool properly with R134a is to calibrate the POA valve for that refrigerant. It makes a world of difference.:thumbsup: I've never found it necessary to install an R134a specific TXV on any of those old systems.

Thanks for the reply but how do you calibrate the POA and/or will just installing the new style with the switch on it says in catalog "converts it to a more reliable cycling-clutch system". And on the TXV assuming it means "thermal expansion valve" for dummy here, how do I know NAPA has the right one since all are probably from same source vendor?

Thanks,

RwS

Thanks for the reply but how do you calibrate the POA and/or will just installing the new style with the switch on it says in catalog "converts it to a more reliable cycling-clutch system". And on the TXV assuming it means "thermal expansion valve" for dummy here, how do I know NAPA has the right one since all are probably from same source vendor?

Thanks,

RwS

Here is the procedure for testing and adjusting the POA valve:
http://www.autoacforum.com/messageview.cfm?catid=20&threadid=16311
You can also send it to a company in FL that will do it for you. The name escapes me right now, but maybe someone will chime in with it.

Found it. Classic Auto Air in Tampa Fl. http://www.classicautoair.com/

Don't replace the POA with an eliminator kit. This is actually a downgrade to the system.
Cycling clutch systems are a series of tradeoffs and actually a piss poor way of doing things. They are mainly used because they are cheap to manufacture and install. The reason the eliminator kits are popular is because many folks don't understand the old POA system. It is far superior to any cycling clutch system made today.

TXV=Thermal Expansion Valve. I'm not sure about the various sources but they are widely available and relatively generic parts. The valve for your Chevelle is likely in use on other automotive systems or even in some refrigeration systems. Listings at Old Air Products, ACKits, NAPA and Classic auto Air don't have refrigerant limitations.
A quick search of the napaonline site shows part number TEM 207300 as the valve you need. About $28.

Thanks to all for the information!

RwS

To: ISRX101

one more question on this is in the procedure it says to adjust the screw 1/4 turn counterclockwise but does'nt give what the pressure should be for 134a?

RwS

To: ISRX101

one more question on this is in the procedure it says to adjust the screw 1/4 turn counterclockwise but does'nt give what the pressure should be for 134a?

RwS

I thought it gave the pressure. 27-28 PSI according to the R134a pressure/temp chart. http://www.csgnetwork.com/r134apresstempconv.html (The original setting is 31-32psi for R12)

I've found they work really well at 26-27 in real life but could cause evaporator icing in certain conditions. The idea is to get the pressure as low as possible but prevent evaporator freezing.

Thanks again ISRX101.

RwS

Thanks again ISRX101.

RwS

Any time Dude. Good luck with your AC.

Everything on a R-12 system works well with 134. I sent my POA valve toTampa Fla. Talk to Curtis.... Shipping, labor, Total price was $33.00.....
My car is a 70 SS 454. Mine is now a 134 A/C.. Works fine....
The big change to make big improvements.... I am thinking about a 134 type condenser. What I have works just fine. DO NOT go for the cycling clutch BS.... The 70 style G.M. systems are NOT DESIGNED to cycle.
Any A/C questions call Curtis at Classic Air in Tampa Fla. If you have an A/C question ask a A/C Tech....NOT Bubba at some parts place.
Bob

Yep. A Parallel Flow condenser will make a big difference on R134a conversions, mostly in the more arid parts of the country. The Deep South and American Southwest especially. It's more efficient than the serpentine type used on cars in the 60-70's. In those areas, updating the condenser is almost a "must do".
In most US climates it's not really necessary on most vehicles, though. It can make a difference, but isn't usually cost effective unless the vehicle had a marginal R-12 system to start with. Dual systems on vans, Fox chassis Ford products, and most small GM cars come immediately to mind for "marginal" systems.
60s-70s Chevelles and other GM cars with the POA, STV, or VIR AC systems will note an improvement with a PF condenser, but the cost of retrofitting usually outweighs the benefit unless the owner is looking for ultimate AC performance under all conditions.

I don't know Curtis at Classic Auto Air specifically, but I know they do a fine job of testing, calibrating and restoring POA valves, Suction Throttling valves, Hot Gas valves and VIR assemblies. Their Customer Service is really good too, from my limited experience with them.:yes:

Where can you buy this PF type condenser for a 69 chevelle?

RwS

http://www.ackits.com/c/Parallel/Parallel+Flow+Condensers+-+Aluminum.html

They are universal fit, so you need to have lines made to mate it to your system. AFAIK, there's no direct fit PF condenser for 60-70's cars.