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do you lose the oil???

notsobrite on Sun June 21, 2009 10:49 PM User is offline

Year: 1994
Make: oldsmobile
Model: cutlass ciera
Engine Size: 3.1
Refrigerant Type: 134a
Country of Origin: United States

Hi, I am thinking about buying a manifold gauge set and vacuum pump. Between myself, wife and kids we have several older cars some of which with ac issues. They all have 134a. I have spent some time reading the Mastercool ac basic service manual. I understand that the correct way to add 134a is to first vacuum the system then add by refrigerant by weight. A couple of questions come to mind. 1. When you deep vacuum a system do you lose pag oil and if so do you add some back, how much and how? 2. When a car (one of my other ones) has max refrigerant of 22.9 oz. do you just guess how much is left in the second 12 oz can.

fonebone on Mon June 22, 2009 1:25 AM User is offline

First, Congratulations for purchasing the Mastercool Manual. You are on the right track for learning about A/C! And get that manifold set and pump when you can-With all those cars, you will save a bundle, and learn to do it right. To answer No.1, no, vacuuming out a system does not pull the oil, just the gases, air, moisture, refrigerant. No.2- we're talking 1.1 ounce over; that is, if you get it all out of the cans, and don't lose any switching cans. I'm sure others here will agree(any one?). As an experiment, when you get the gauges, add the R-134 with just a tad left in the last can. Leave it connected. Monitor the pressures, let the system stabilize for a few minutes at about 1500 rpm. Leave a digital temp in the center vent in the car. Note the reading. Add that tiny bit more and see if the high side goes too high, meaning over max pressure for ambient temp that day(it's OK to hit max for the ambient that day), see if vent temps stay at the coldest(my guess--they will). If it climbs slightly higher, you are a tad over charged-don't panic, it WILL leak out soon enough.

Chick on Mon June 22, 2009 6:40 AM User is offlineView users profile

As stated above, vacuum will not remove the oil, but some does come out with the refrigerant, so if you're not replacing any parts, It is safe to add a half ounce to an ounce doing it for the first time.. As far as the last can goes, you'll lose some charging from can to can, so when you get to your last can, you are gonna wind up using half of it anyway..Depending on the length of your hoses it could hold as much as three ounces right there.. you'll get used to adding it, and with O tube systems always feel the inlet and outlet of the evap, should be the same temp, with the outlet just slightly colder, then you're fully charged.. Hope this helps.

Email: Chick


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