Automotive Air Conditioning Information Forum

A couple of questions concerning what I have found so far:

When I drained the old compressor…..not a drop of oil came out. The clutch disk spun freely and I could hear and feel that it was still pumping. Is that unusual to have no oil in the compressor?

I was curious how much oil was in the accumulator so I cut it open and it too had no oil in it and the desiccant bag when squeezed did not have much in it either. Is that unusual and what does that signify?

I got the new compressor installed on the truck along with the suction and discharge line. The two lines are not connected and still have the two caps on the two fittings. I only put 4.5 ounces of oil in it because I didn’t want to risk losing some, while getting the suction and discharge line manifold connected to the compressor, and therefore not having an accurate account of the amount of oil.

With this truck, the manifold has to be connected before the compressor is mounted because of the limited space to work in so I also had to be very careful not to get any debris on the manifold mounting area at the same time.

I also got the fan and radiator shroud back on and got the new condenser installed with the caps still on the two fittings.

kenlou wrote: Mon Jun 30, 2025 7:57 pm When I drained the old compressor…..not a drop of oil came out. The clutch disk spun freely and I could hear and feel that it was still pumping. Is that unusual to have no oil in the compressor?

It's not unusual. For lubrication, some compressors rely on oil that's carried continuously throughout the system by the refrigerant. On the other hand, some compressors retain some of the oil. It depends on the design.

Unfortunately, there's no dip-stick to gauge whether a system has the recommended amount of oil in it. The only way to tell is to start with a "dry" system and add the oil from there according to the manufacturer's specifications—either by adding it all to the compressor (if it will accept it) or by "oil balancing" the system, whereby a certain amount is added to each component.

kenlou wrote: Mon Jun 30, 2025 7:57 pm I was curious how much oil was in the accumulator so I cut it open and it too had no oil in it and the desiccant bag when squeezed did not have much in it either. Is that unusual and what does that signify?

The accumulator should have "some" oil at the bottom. Could be that the system was low on oil to begin with.

I want to double check and try to get confirmation that I am proceeding correctly with this project. The truck is wanting 9 ounces of pag oil. I am replacing EVERYTHING but the evaporator:

1. Using the Rotunda A/C Test Fittings connected to the evaporator inlet and outlet tubes and connected to my gauge set, I ran the vacuum pump for two hours and the gauge read (30 in-Hg). The evaporator has been sitting in a vacuum for more than a week now with no movement in the gauge. The evaporator should be good…..CORRECT?
2. I drained the new compressor and added 4.5 ounces into it and spun it 10 times to get it circulated in the compressor…..CORRECT?
3. I will add 1.5 ounces into the inlet of the condenser…..CORRECT?
4. I will add 1.5 ounces into the inlet of the accumulator…..CORRECT?
5. I will add 1.5 ounces into the inlet of the evaporator…..CORRECT?
6. When I flush the evaporator I will back flush it…..CORRECT?

Kenny

kenlou wrote: Thu Jul 03, 2025 9:45 am 1. Using the Rotunda A/C Test Fittings connected to the evaporator inlet and outlet tubes and connected to my gauge set, I ran the vacuum pump for two hours and the gauge read (30 in-Hg). The evaporator has been sitting in a vacuum for more than a week now with no movement in the gauge. The evaporator should be good…..CORRECT?

Not necessarily. Vacuum testing is only 50 percent of the equation. The other 50 percent is pressure testing. Bear in mind that a component that holds vacuum might leak under pressure, and vice-versa. Chances are, the evaporator is good, though.

kenlou wrote: Thu Jul 03, 2025 9:45 am 2. I drained the new compressor and added 4.5 ounces into it and spun it 10 times to get it circulated in the compressor…..CORRECT?

That procedure is normally correct as long as the compressor has been installed (along with everything else), just before pressing the button, and the system is ready to run. The theory is to clear the chambers above the pistons of any oil so that the compressor doesn't "try" to compress a liquid, which can't be compressed, and break something internally, like a connecting rod. Discussions have it that both ways are acceptable without any consequences, although I prefer the "fully assembled" method.

kenlou wrote: Thu Jul 03, 2025 9:45 am 3. I will add 1.5 ounces into the inlet of the condenser…..CORRECT?
4. I will add 1.5 ounces into the inlet of the accumulator…..CORRECT?
5. I will add 1.5 ounces into the inlet of the evaporator…..CORRECT?

The amounts described in Steps 3 through 5 sound good, part of the oil balancing method, and should work. Alternatively, you could consider allowing a little more oil for the accumulator (because it's larger in volume than a typical R/D), a bit less for the compressor, changing the amounts as follows: Compressor, 4.0 fluid oz.; condenser, 1.0 oz.; evaporator, 1.0 oz.; accumulator, 3.0 oz.

kenlou wrote: Thu Jul 03, 2025 9:45 am 6. When I flush the evaporator I will back flush it…..CORRECT?

Sounds good. Be sure to dry out all traces of the flushing solvent using nitrogen or (lacking an N2 set-up) clean and dry shop air.

Thank you very much, John. I will have more questions as this project continues on.
The heat and humidity here are slowing me down.

I managed to get both compressor lines connected to the condenser and to the accumulator. I am also using nylog blue on all o-rings and threads. My next step is to get that evaporator flushed.

I wasn’t going to mention it but if it seems like this project is turning into a hobby, the main reason is that I am a caregiver to my Down syndrome brother that is wheel chair bound and I work on it when I can. I am retired so I am in no big hurry but I am slowly getting there.

The heat and humidity here in Central Illinois also does not help.

Kenny

I removed a plastic protective cover on the firewall and located the condensate drain. The system did have the green dye in it but with my light and glasses I checked the area once it got dark and I see no trace of dye anywhere in that area, so that is a relief.

kenlou wrote: Thu Jul 03, 2025 3:57 pm I managed to get both compressor lines connected to the condenser and to the accumulator. I am also using nylog blue on all o-rings and threads. My next step is to get that evaporator flushed.

Using Nylog Blue is always a smart move when assembling a system. Flushing the evaporator should be relatively straightforward.

kenlou wrote: Thu Jul 03, 2025 3:57 pm I wasn’t going to mention it but if it seems like this project is turning into a hobby, the main reason is that I am a caregiver to my Down syndrome brother that is wheel chair bound and I work on it when I can. I am retired so I am in no big hurry but I am slowly getting there.

Learning as you go and treating your project as an (enjoyable!) hobby are commendable. You might make a few mistakes along the way, but that's part of the learning process, as long as you maintain safe practices. Pressurized refrigerant can be hazardous, especially to the eyes, so be sure to always wear protective glasses.

All the best to you and your brother.

kenlou wrote: Thu Jul 03, 2025 3:57 pm The heat and humidity here in Central Illinois also does not help.

It's the same now in my neck of the woods. Makes one appreciate a good MVAC (Mobile Vehicle Air Conditioning) system even more.