PAG Oil Max/Min System Capacity

Information on some common auto air conditioning topics.
Archived Forum

Moderators: bohica2xo, Tim, Dougflas, HECAT

m240b
Posts: 5
Joined: Thu Jul 18, 2019 4:37 pm

PAG Oil Max/Min System Capacity

Postby m240b » Thu Jul 18, 2019 5:04 pm

Greetings everyone,

New to the forum and I am currently attempting to repair the a/c system on a 2005 Honda Civic LX. I will be replacing all of the a/c components except the a/c lines which I have flushed. The issues that I am currently trying to figure out is how much total pag oil to add to the system. The paperwork that came with the new Four Seasons compressor says that it comes pre-filled with 3oz of oil. If I were to install all the components as they are I would only have 3oz of oil in the system. Where do I find how much more or less I am supposed to add? The repair manual I found online only tells me how much to add if I am replacing single components, not all of the components at the same time. I would greatly appreciate any input.
User avatar
JohnHere
Posts: 151
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate

Re: PAG Oil Max/Min System Capacity

Postby JohnHere » Thu Jul 18, 2019 7:42 pm

My reference material for your vehicle specifies 18 ounces of R-134a and 5 ounces of PAG-46.

Since you don't know for sure how much oil (if any) is in the new compressor, I would drain it out and start from scratch. You have all new components, so you could distribute the oil among them as follows: 2.5 ounces in the compressor, 1 ounce each in the evaporator and condenser, and 0.5 ounce in the receiver/dryer. Alternatively, you could put all 5 ounces in the compressor, if it will take it, and let the refrigerant distribute the oil throughout the system components.
m240b
Posts: 5
Joined: Thu Jul 18, 2019 4:37 pm

Re: PAG Oil Max/Min System Capacity

Postby m240b » Fri Jul 19, 2019 6:13 am

Thanks for the help.
User avatar
JohnHere
Posts: 151
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate

Re: PAG Oil Max/Min System Capacity

Postby JohnHere » Fri Jul 19, 2019 7:25 am

Good luck with your project, and let us know how it turns out.
m240b
Posts: 5
Joined: Thu Jul 18, 2019 4:37 pm

Re: PAG Oil Max/Min System Capacity

Postby m240b » Tue Jul 23, 2019 5:49 am

Greetings once again!

As you can tell from the exclamation point in the above greeting my a/c repair was a success. The most difficult part of the whole repair was connecting the a/c lines to the expansion valve through the firewall. To accomplish this my brother used a couple of 3/8 socket extensions to push from the outside, meanwhile I was inside under the dash board pushing outward on the expansion valve while keeping it aligned. Another very frustrating part was connecting the a/c lines to the condenser due to the very limited amount of space. Pulled vacuum for 45 minutes and verified that the vacuum held, then I proceeded to try and recharge the system with refrigerant correctly. During the charging process I noticed that the pressure on the high and low side where the same even though the compressor was running. I was disappointed in what I thought was failure and as I gave up and reached to close the manifold gauge valves and call it a day I noticed that as I closed the high side valve the pressures began adjusting correctly. It was a one of those moments where you feel like an idiot, of course it wasn’t working you had the high side valve open the whole time. In the end I charged the system and the a/c blows nice and cold now which is great because this Houston heat and humidity is brutal. Thanks again for the help!
User avatar
JohnHere
Posts: 151
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate

Re: PAG Oil Max/Min System Capacity

Postby JohnHere » Tue Jul 23, 2019 6:54 am

I'm certainly relieved that you noticed the open high-side valve in time. Otherwise, you would have had an exploding refrigerant can at some point...a very bad situation for obvious reasons.

As a safety reminder, always ensure that high-side gauge-set valve is closed whenever the compressor is running, keeping the refrigerant can upright, and charging gas-only (not liquid) through the low side.

Also glad you figured out a way to get everything connected at the firewall and under the dash. That's often a challenge. Best of all, the system is now running well and you're driving in cool comfort again.
m240b
Posts: 5
Joined: Thu Jul 18, 2019 4:37 pm

Re: PAG Oil Max/Min System Capacity

Postby m240b » Thu Jul 25, 2019 5:58 pm

Greetings,

Unfortunately the a/c on this 2005 Honda Civic LX was not fully repaired. The a/c worked great for 2 days but on my drive back from work I was stopped at a train crossing and noticed the air was getting warmer and eventually was just hot. The green light on the a/c button was off and would not turn on. When I got home I connected the manifold gauge to check out was was going on. My first static readings were Low-Retard and High-135. When I turned the car on and turned the a/c all the way up my readings were Low-50 and High-190. I read that it may be expansion valve that is not working correctly. Eventually after running the a/c for a while the readings were Low-40 and High 200. I turned the car off noticed that the pressure was not equalizing like it did before. I timed it to see how long it was taking to equalize and I gave up at around 1 hour and 10 minutes but it was almost there. I would really appreciate some help and thanks again.
User avatar
JohnHere
Posts: 151
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate

Re: PAG Oil Max/Min System Capacity

Postby JohnHere » Fri Jul 26, 2019 10:33 am

I'm going to backtrack and ask a few questions.

You didn't mention why you replaced all the major components. Did you have a catastrophic compressor failure that sent debris through the system, or did the compressor just wear out and fail to "compress" sufficiently anymore? Was it because of refrigerant leakage from the front seal or elsewhere? Or some other reason(s)?

After repairs, how did you evacuate and re-charge the system? Did you use a good vacuum pump...not a venturi-style pump that runs on compressed air...to draw it down to at least 29 inches of mercury (In. Hg.)? Did you use 12-ounce cans of pure R-134a (without any stop-leak, I hope) and estimate the charge, or did you measure the exact amount using an accurate refrigerant scale or A/C machine? Even going back to 2005, an A/C system's charge that's a little "off," even by an ounce or two, can adversely affect performance.

You didn't mention the cooling fan behind the condenser and radiator. Does it seem to be working okay in that when you're stopped with the A/C system running, the fan is roaring away at a high speed, especially with the summer temps in your area being in the mid-90's, at least. Also, is the fan rotating in the right direction; that is, is it pulling air from the front of the car toward the rear, through the condenser and radiator, and not vice-versa?

When it stopped cooling, did you check under the hood to see whether the compressor was still running?

So when you got home, you were able to turn on the system by pressing the A/C dash button, which then illuminated normally, unlike your previous stop?

Your static and dynamic pressures don't look too bad, although the low side is elevated. So, yes, it could be a faulty TXV. But I suspect that it's more likely an airflow problem over the condenser. Assuming that you did everything else correctly, I would check that first.
m240b
Posts: 5
Joined: Thu Jul 18, 2019 4:37 pm

Re: PAG Oil Max/Min System Capacity

Postby m240b » Fri Jul 26, 2019 9:37 pm

Yeah the system had been down for about a year. My family member said that a mechanic told him the compressor was bad but I wanted to verify. I found a 7th Gen Civic repair/maintenance manual and followed the troubleshooting guide. Verified the a/c circuit was good all the way to the compressor coil which did not measure correct resistance. I decided to replace the whole compressor. While researching I wanted to verify that the compressor had not contaminated the system and I stuck a shop towel into one of the a/c line and sure enough it had this grayish powder. I decided I would replace all the major components to be on the safe side except the a/c lines which I flushed out. Once all the replacement components where installed I pulled a vacuum with an FJC 6905 1.5 CFM Vacuum Pump for 45 minutes. The vacuum pulled all the way down to 30 inches of mercury. After the first 45 minutes of pulling a vacuum I closed off the valves turned off the pump, the vacuum held for another 45 minutes successfully. I used the 12oz refrigerant cans with no oil or stop leak additive. I used a food scale to measure the amount of refrigerant I was adding, this step was troublesome because it was difficult to get a consistent weight. I charged it as best I could with the food scale and it worked great initially. This may be the issue since the tolerance for the refrigerant is so small I may have screwed it up. The fan appears to be working fine. Turns on when I turn the a/c on. I did not check the compressor when it stopped working to see if the clutch was engaged. When I made it home and got around to checking it again the a/c turned on and was working again. The strange part is that it seems to be working fine now. I used a thermometer to measure the temp and it was down to 62F while parked in the driveway. How long is it supposed to take for pressure to equalize after you turn off the car because I waited for an hour and ten minutes and in that time it came close but did not equalize. I can’t think of anything that would be obstructing flow for the condenser but I will check again just to make sure. Once again thanks for the help this has been a great learning experience.
User avatar
JohnHere
Posts: 151
Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate

Re: PAG Oil Max/Min System Capacity

Postby JohnHere » Sat Jul 27, 2019 10:27 am

Verified the a/c circuit was good all the way to the compressor coil which did not measure correct resistance. I decided to replace the whole compressor.
That's fine, because the clutch assembly probably would have cost almost as much as the new compressor.
While researching I wanted to verify that the compressor had not contaminated the system and I stuck a shop towel into one of the a/c line and sure enough it had this grayish powder. I decided I would replace all the major components to be on the safe side except the a/c lines which I flushed out.
The gray powder usually comes from the compressor's seals wearing out. So the compressor probably was at or near the end of its useful life.
...I pulled a vacuum with an FJC 6905 1.5 CFM Vacuum Pump for 45 minutes.
That's good. But if I'm not under any time constraints, I let the vacuum pump run for at least a couple of hours.
I used a food scale to measure the amount of refrigerant I was adding, this step was troublesome because it was difficult to get a consistent weight. I charged it as best I could with the food scale and it worked great initially. This may be the issue since the tolerance for the refrigerant is so small I may have screwed it up.
When charging using a refrigerant scale, the scale will count down and let you know precisely how much refrigerant enters the system. With a food scale, your charge might be off a bit. Also, you should purge air from the yellow hose each time you connect a 12-ounce can. Otherwise, any air in the hose will wind up in the system, compromising cooling efficiency and raising pressures.
I used a thermometer to measure the temp and it was down to 62F while parked in the driveway.
If that reading was the center vent temp, it's not cooling very well. Parked in the driveway with the A/C system running for ten minutes or so, the engine at around 1,800 RPM, blower on medium and in "recirc" mode, I would expect to see vent temps somewhere in the 40's depending on the ambient temperature and how warm the car's interior is.
How long is it supposed to take for pressure to equalize after you turn off the car because I waited for an hour and ten minutes and in that time it came close but did not equalize.
I'm not sure. Sounds like a long time. But if it eventually equalized or came close, the TXV is probably working.
I can’t think of anything that would be obstructing flow for the condenser but I will check again just to make sure.
Check that the fan shroud and any air seals are in place and that the fan is running at full speed when it's sitting still in the driveway with the A/C on as above. You could also try spraying the condenser with water while watching the gauges to see how the system reacts. A dropping vent temp and pressures would point to an airflow/condensing issue. If you still can't determine what's going on, I recommend taking it to a professional A/C shop for further diagnosis.

Return to “Automotive Air Conditioning Procedures, Tips and FAQ.”