AC high side fitting

[Jeff Moffo]

Hi everyone,
I am trying to run a vacuum on my r12 system in my '76 in order to perform an evacuation and see if it holds vacuum. I didn't realize the high port is slightly smaller than the low port. I'm guessing it is 3/16 make thread vs the low side which is 1/4.
Is there an adapter available SOMEWHERE so I can use the manifold hoses I have?
They fit the low side perfectly but are slightly too large to fit the high side. 
Any advice would be helpful. Thanks!

[Scot Minesinger]

Yes, NAPA or Aireco probably have that adaptor - try Amazon

[Jeff Moffo]

Thanks, Scott. What is it "called"? I'm guessing "R12 high side adapter"!?

["Cadillac Kid" Greg Surfas 15364]

3/16" female flare to 1/4" male flare adapter.
Greg Surfas

[Jeff Moffo]

Thanks. Autozone had it!! Works perfectly. 

[TJ Hopland]

Is this because automotive used the different size fittings and he had a standard manifold gauge set?

["Cadillac Kid" Greg Surfas 15364]

1/4" flare has been the standard size refrigeration fitting for gage ports.  My guess is that they went to a 3/16" fitting on the discharge line which needed that adapter (J-24598) which was on the dealer's charging stations to be sure the high side and low side were not switched (on the gages).  That's my guess
Greg Surfas

[Jeff Moffo]

Sounds logical enough. Unfortunately the old girl won't hold vacuum overnight after I evacuated and pulled a vacuum. Now, comes the hard part.

["Cadillac Kid" Greg Surfas 15364]

Jeff
The system should be tested under pressure. That way you can find the leak with either soap bubbles or a leak detector
Greg Surfas

[Jeff Moffo]

Yes. Done have suggested actually filling it with 134A to test for leaks but that doesn't sit well with me. Others suggest using an air compressor to fill it with air to do a pressure check. Any thoughts?

["Cadillac Kid" Greg Surfas 15364]

No if you are currently using R-12 and have Mineral Oil in the system DO NOT use 134a to pressurize the system.  I personally use R-22 to test my R-12 systems for leaks.  It reacts better with my leak detector to positively identify leaks.  Nitrogen is also an acceptable but extreme care must be used to be sure and limit the pressure to less than 100 psig.
Greg Surfas

[Jeff Moffo]

Someone was going to help on this project and when they suggested 134A, I backed away seeing it was R12.  Is R22 readily available? 

["Cadillac Kid" Greg Surfas 15364]

Yes but you DO need to be liscenced.
Greg surfas

[Jeff Moffo]

I figured as much. At least I have a starting point when I can find mechanic in the area that can help me. Often times, the first response is, "Just convert it to 134A".🙁

["Cadillac Kid" Greg Surfas 15364]

Jeff
I tried 134a in my '76 and the best I could do was around a 25%reduction in capacity. Here in So. Texas when in heavy summertime traffic that resulted in 50+ degree air out the vents. Without going into detail the VIR system is very precision and 134a confuses the components resulting in poor performance.
Greg Surfas

[Scot Minesinger]

Well I never had a VIR R134 system (1973-76) in VA let anyone down, they all thought they were wonderful ac cooling results.  That is Virginia and at most 95'F and humid is about the worst it gets here.  Since 2015 no R134 is used, so it is being phased out - Might as well use r12, although r134 is still low cost, just bought a 30lb drum for $115.00 (less than $4/lb).

There is no way you can use r134 to pressurize a 12 system - do NOT do it.

Greg, why no more than 100psig with Nitrogen?  I have seen it done to 200psig with Nitrogen on an R12 Cadillac system, not that was a good idea (I have not done it), just wondering what the issue is.

["Cadillac Kid" Greg Surfas 15364]

Scott,
No real need .  A leak will be apparent at 150 psig.
Greg Surfas