I need a 20/80% vacuum valve for a 1964 Cadillac Convertible De Ville

I am hoping for some help --from my Cadillac guys

Been thru the regular channels --ebay -old air products --caddy daddy

Is there a place that rebuilds the vacuum valves ?

Any help locating this item is greatly appreciated
Will need a price quote



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Not sure how much you found one for, but theirs one on ebay for $83.28 free shipping

Joe D

Thanks for the lead


Tony it's unfortunate that the person you talked to would make such an outrageous statement about 134a refrigerant. The whole world has changed to this stuff and some how he states it doesn't get as cold? Totally bad information that gets ranked up there with the best urban myths spread by the internet. 134a will freeze a condenser to a block of ice. How much colder than that do we need to be? This is why we install an stv update kit. The kit senses when the condenser starts to FREEZE and shuts off the compressor to THAW it out. It cycles the compressor so that you don't get a block of ice inside your dash from the 134a.  

Here is the problem, people won't pay to have their systems torn completely down and rebuilt. They cobble parts on, it leaks, condensors plug off, stv and sop valves are not calibrated, update kits aren't installed and blowers weaken, ductwork leak on and on. This is why I tore my system completely apart to fix it once and do it right. 

As I've said before you can add propane to our a/c systems and it will work. It's just a tad dangerous. 

Our systems are well over 50 years old. If you want it to work right it needs to be totally rebuilt. Just like a worn out engine you can't just add new pistons and nothing else. It would still be a piece of crap.

  •  Clovis

My circumstances are a bit different than many others —as my AC system has had upgrades and maintained as needed over the years and I know the cars entire history 

I am prepared to change anything that may be needed —including everything if needed

I have never had any kind of problem with the evaporator  valve freezing on me and I do not have the STV upgrade installed with my 134a

not at all sure how —the lack of the STV upgrade is effecting the system 

i only get about 50 degrees at the vents so —my system —may not be getting cold enough to freeze anything at this point ( 32 degrees -is still freezing right ! )

the best temps I remember  SB in the mid to high 30’s  at the vents 

your thoughts are always appreciated as I believe you know by now 


Don't listen to everything that I say Tony. I keep calling the evaporator a condenser LOL

When i am speaking to someone --who is an Expert on a given subject- ( as in old air products ) and they voice an opinion i will have a tendency to have a higher regard for that opinion more than that of someone less knowledgeable about a given subject ( as in an authority on a subject )
I am in no way indicating it is you who is less knowledgeable about the subject in any way at all
I have seen you go off on this --internet myth rap you have --when you do not like what you hear or are questioning the info we are talking about
I respect your position-- on 134a doing exactly what you need in the very fresh all new AC system you have created in you ride
I do have to say it is not the first time i have been told the R-12 freon produces colder AC temps than the 134a in the same system over the years
I am very happy for you ( really ) that your AC system is performing to your expectations and you took the time to post the best thread on the subject to date to help many-- get the courage -( including myself ) to get the comfort control to work as it should again
I do not think --repeating --what an AC authority on the subject has told me --is spreading an internet myth -but just relaying his opinion on his expertise to others

I would be happy to explain the difference in the two freon temps --as i will be making the change from 134a to R-12 if all goes as planned ( stiil in planing stage )
But i cannot really do that as my current system --does not have the STV update --it should have so my 134a system is not performing as it SB without that part installed
I know the pressures my system is performing at are --not correct --without the STV update and attribute that to my vent temps not getting cold enough
If it is parts replacement preventing reaching better vent temp - that will be addressed

I do feel good about getting the system back to the way it was designed
Being able to aquire the R-12 just happened by chance for me


Pls explain the prep work you did on the heater motor cover
the darn things looks brand new


Joe D

Got the valve you suggested
Thanks again


You know --i think we can both agree that both 134a and R-12 can be effective in getting our comfort control to work as it was intended to do

Condenser - evaporator --evaporator --condenser --thermostat ( themistat )
So the you go- you 64 Cadillac owner --you ! ! LOL !!

Tony you hit the nail on the head with the comment "r12 is colder in the same system". That is a large portion of why the 134a is not going to get as cold because the stv has not been 1) adjusted to the proper pressure for 134a or 2) an update kit has not been installed. The system can't stay the same for it to work it's best. I've actually stocked up on 134a because it's soon to be outlawed just like r12. The unfortunate problem is people are thinking they are getting r12 and they are being ripped off. R12 being outlawed is kinda like black market commodities, you never know if your getting the real thing or a knockoff.
There are many gases that will work in a refrigeration system. Some more efficient, others not so much and some very explosive.

If you end up doing the stv update go to rock auto and get an adjustable kit. The ones they sell at old air products and other places is not adjustable. This way you can adjust how often the compressor cycles off and on getting the coldest temps from your vent as possible. If you find your evaporator (Mark would be proud, I finally got it right) freezing up then you can increase how often it cycles to prevent the freezing.

I cleaned the blower case with elbow grease. I am fortunate to have a very rust free car. 


I recommend you to check the function of the 80/20 valve before install. I bought a new valve last year that didnt work properly, the actuator arm didnt move at all when vacuum was applied to the 20% port.


Two Simple considerations for me when I go back thru my AC:
1. Is R12 cold enough if system is in good order?  Yes
2. Will R134a be phased out and become obsolete and expensive like R12 did in the past? Yes
So... Dino stays R12.



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