Automotive Air Conditioning Information Forum

Injectors are available that will allow you to add the oil without having to break the vacuum or disassemble anything.

Are you talking about the ones that typically hold 2 oz?

Yes, that's one type. There are larger ones, though.

As I mentioned to someone else on the Forum the other day, if your daily temperatures are in the 40-50°F range, like they are in my area, it's too cold to weigh-in a full charge unless you set the charging cylinder in warm water to raise the refrigerant's pressure, use an electric cylinder warming blanket, or you have a heated shop. If not, charging it partially to get positive pressure in the system is a good plan. Just make sure that you write down the precise weight you put in it now so that you can follow-up weighing-in the rest of the refrigerant in the Spring.

Per John,
"As I mentioned to someone else on the Forum the other day,"....

I have often commented that serious DIYers would be well served if they followed along on as many posts as they can on this forum. Various questions arise and the advice from Tim's superstar line-up of experts cannot be beat. You can learn something from every thread, believe me.

In fact for the truly serious, I again advise DIYers to step back thru the archives one page at a time and significantly expand your knowledge base.

I must add that while your personal refer consultant suggested installing liquid 134 into both hi and low sides, please know that this is only acceptable on an empty non-running system such as yours. You would NEVER add liquid 134 to the low side on a running system, you will blow the comp.

Also, personally, if I were to use an oil injector as described, I would only be adding oil to the high side. I would not want to have a big glug of oil sitting in the low line just waiting to be sucked into the comp

JohnHere, I do have a heated garage that I keep at 60 degrees, but I plan on only a partial charge. I will finish the rest in the spring.
I have a digital weigh scale that I will use to weigh the charge.

Questions:
1. So, tbirdtbird, when adding the refrigerent, I can add the full contents of two 12 oz cans strictly as liquid?
2. Do I inject the 4 oz of oil before the refrigerent? The injecter I am getting has only a low side quick connector adapter so I will have to remove one of the
switches mounted in the high pressure liquid line to be able to screw onto one of those ¼” valves. Would that be OK?

Sorry to jump into a thread that's been running a long time, but I'm still doing it

I'd suggest dumping the oil into the high side as you said and then pulling vacuum on the low side, oil has a lot of dissolved air in it, best to get it out. I've had various glass accumulators and other vessels in my labs over the years, trust me when I say that PAG looks exactly like a tall glass of cold beer when freshly poured in and being put under vacuum. It will bubble like mad at first and then a steady stream of tiny bubbles for an hour.

Haven't read enough of the thread to have any other opinions...

DetroitAC, the system is sitting in vacuum right now. How would I pull a vacuum on just the low side?

Thanks, Detroit, very helpful. I did not know that. Your comments are always more than welcome.
Yes add the oil before the 134 but re-pull the vacuum as Detroit suggests first before adding the 134.
When you are ready to add 134, I personally would install as liquid to the high side. It wont stay liquid very long but it is a fast was to get it in there. No need to install to both sides.

Do you have a heat gun or hair dryer you could gently play on the cans, because as soon as they cool off, the 134 will stop coming out. Think about a can of computer duster air, it quickly chills and then no more refrigerant mist comes out...ie there is not enough heat to boil off the refrigerant (which happens to be R152). Some use a warm water bath to put the cans in, but this is harder to do if you use a side tapper, see below.

Today's freon cans have a so-called self sealing fitting, which like so many other things the EPA has ruled, do not work, and require a special tapper. And we assume you are using cans of pure 134 without any additives. Those appealing cans of freon in the parts stores with the fancy hose , fancy printing, and fancy promises of stopping leaks and curing cancer, are to be AVOIDED at all costs, they will ruin your system, and should be outlawed.
So use a side tapper. That way you can use your regular MGSet hoses. Tim has them. Hold can upright and put the tapper on the very bottom

My injector came only with a low side fitting, and I changed it over to a high side fitting, but I don't remember what I did, I'll have to check it out.
Why the manufacturers of these things think it is a good idea to inject oil into the low side of a running system is beyond me....most people do NOT want to slug their compressor with oil or any liquid. Perhaps JohnHere could comment.

"DetroitAC, the system is sitting in vacuum right now. How would I pull a vacuum on just the low side?"

Only open the low side handwheel on your Manifold Gauge set (MGS)