R-134a oil injector?

Bonnewagon

Geezer
Sep 18, 2009
8,025
113
Queens, NY
Anyone use a GOOD yet inexpensive oil injector for R-134a systems? I have had some over-charge situations where the relief valve opened and lost a copious amount of oil. I need to be able to re-introduce the PAG oil easily. Prices are all over the place yet they mostly look the same. I am seeing videos where these guys remove the schraeder valve on the high side, pull vacuum on the low side, jam a rubber tube into the high side port, and stick the other end into a container of PAG, sucking it in. Do they not realize moisture laden air is also being sucked in? Or do they know to deep vacuum all over again? Yikes!
 
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Bitterman

Greasemonkey
Jan 17, 2017
209
43
My local autozone has an oil injector AC tool as a loaner tool. It's a $100 deposit for the tool and I have had success when I have used it. Cant get any more inexpensive than free. Not sure what other chains have for loaner tools but it may be worth a look.
 

Bonnewagon

Geezer
Thread starter
Sep 18, 2009
8,025
113
Queens, NY
As much as I like free, I would be suspicious of what oil was used before I used it. A thorough cleaning would be in order first. I prefer to have my own tools on hand. Borrowing or renting is always at the wrong time anyway. I like this Mastercool unit but I wonder which is best. Using vacuum/pressure to inject oil- or the type that squeezes the oil out as you turn it.
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Bitterman

Greasemonkey
Jan 17, 2017
209
43
I completely understand. My experiences are with the you turn it style. It's worked well for me.
 

ck80

Comic Book Super Hero
Feb 18, 2014
2,811
113
I'd think the vacuum type would be more likely to get closer to the measured amount in, while the turn/plunge you wonder if the exact amount went all the way out or not.
 

Bonnewagon

Geezer
Thread starter
Sep 18, 2009
8,025
113
Queens, NY
My concern is more about allowing air into the already vacuumed down system. The MasterCool instructions seem to address that. Still, you must open the container and add oil or dye. But if you fill it the amount of air is pretty small. I also like being able to just leave the injector attached to my gauge set. Most of the time I am not adding oil but when I need to it will be right there ready to go. This is the arrangement they use. As you can see it is possible to close the valves and work around the oil until needed.
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81cutlass

Comic Book Super Hero
Feb 16, 2009
3,534
113
Western MN

81cutlass

Comic Book Super Hero
Feb 16, 2009
3,534
113
Western MN
It's 3oz of oil, how much do you need?

Are you sure it let out copious amounts or was it just mist and seemed like a lot?
 
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