Problem tapping cans of R-134A

[RossL]

I cannot seem to get a tap that will work with the newer cans of R134A. I had the tap with the point (for the older cans), I bought a new tap that has a flat spike................. I also bought an "adapter" (blue plastic screws on the can), I tried both taps with the plastic adapter

I can't seem to get the R-134A to flow out of the can into the yellow hose on my gauge set. I tried a couple of different (new cans of R-134A) with the same results

[msrichmond]

I have been fighting this too. I had a T-handled can tap for the newer cans that I returned because it apparently requires some kind of dance of all the way in, part way out. I replaced it with a thumbwheel can tap wit a blunt end and what appears to be a star-shaped valve to point toward the yellow hose. Then my yellow hose has a somewhat blunt thing sticking out but then I also have a adapter that goes on the end of the yellow hose (?) and has a pin for that star shaped valve?

In any event, all I can get is a little gas, very few ounces and a ton of frustration.

[JohnHere]

OP, if you have a newer can tap with a flat pin (not sharply pointed) inside, then screw it directly onto the can without the plastic adapter, which isn't needed in this instance.

[tbirdtbird]

OK, what y’all need to recognize is that the newer cans of 134 with that crazy top fitting gives everyone trouble. What you need to do is get yourself a side tapper tool and forget those crazy tops. Use the side tapper at the top. If you want vapor hold the can upright, upside down if you want liquid 134. Have a better day!!!
You can get this tool from Tim here at ackits.com

[msrichmond]

OK, what y’all need to recognize is that the newer cans of 134 with that crazy top fitting gives everyone trouble. What you need to do is get yourself a side tapper tool and forget those crazy tops. Use the side tapper at the top. If you want vapor hold the can upright, upside down if you want liquid 134. Have a better day!!!
You can get this tool from Tim here at ackits.com

When do you want vapor and when do you want liquid?

[tbirdtbird]

You use vapor to charge to the low side. You never want to charge liquid to the low side, you will blow the comp. Liquid cannot be compressed. The hydraulic principle states that you cannot compress a liquid. That is why all the heavy earth moving equipment like bulldozers and such, along with many other applications, use hydraulic cylinders to get work done.

Under certain circumstances you can charge liquid to the high side, but as John already stated this can have consequences and is not advised for the inexperienced, so I will not go into it any further

[msrichmond]

...

Under certain circumstances you can charge liquid to the high side, but as John already stated this can have consequences and is not advised for the inexperienced, so I will not go into it any further

I appreciate the desire not to contribute to or encourage the clueless to hurt themselves. This isn't an economic question for me, I could pay someone to use their $3,000 machine to solve my problem.

But in my case, I have a hobby pretending to be a car, and this project to add AC to a 50 year old Fiat has been enormously satisfying from a hands-on and intellectual point of view.

I have spent a lot of time searching on this topic, and I've seen two things: 1) don't use liquid on the low side. 2) "I've done this (high side liquid with the engine off) forever with no problems".

Even here I have not seen anything detailing the kinds of things that can happen if one uses liquid R134a. So I accept that you are both offering well-intentioned advice from hard-earned experience. But please consider just adding to the knowledge base on this topic.

[Tim]

I know what the book says. I charged 90% of the vehicles with liquid on the low side—just not compressors with service ports directly on the compressor. When charged fully, the low side has liquid refrigerant flowing through it. The issue with low-side charging is slugging the compressor with liquid refrigerant. So slowly add liquid through the low side and be sure you're not attached to the compressor.

[tom216]

I've read, when charging with liquid on the low side, to not exceed 40 psi. use the manifold valve to throttle it down.

[tbirdtbird]

TIM, I am surprised to see that you charged liquid to the low side.

I restored a 1955 Good Humor ice cream truck and did the refrigeration of the freezer box myself, with the assistance of a friend who is a refrigeration engineer by training. I could get that freezer box down to minus 40 degrees F.

Refrigeration is not that different than auto AC. A couple extra parts, maybe. Refrigeration engineers marvel at auto AC because of the variable speed of the compressor, and this was the challenge with auto AC in the beginning.

Residential AC and auto AC are was is termed high level refrigeration.
Mid level is home refrigerator
Lo level is a freezer down to -30
Ultra low is below -30

Anyway my refer engineer buddy told me to charge liquid to the high side until it will not take any more, and then finish off with vapor to the low side engine running at 1500 rpm if needed. I use a scale to follow the liquid weight installed, and also the amount of vapor installed. I almost never need to add any vapor.

Sorry for the long reply.