AC recharge after heater core replacement

[bryansr]

I have to admit, I feel like I'm in a little over my head here.....

I did the dreaded heater core replacement on my '98 EB in December (a big job, but not bad once I got into it), and decided to wait until warmer weather to recharge the AC.... So now I'm ready to recharge it and going to replace the o'rings I'd had loose (3 on the upper hose to the accumulator, 3 on the lower hose by the orifice tube, and 1 behind the accumulator nut) along with a new orifice tube. I see it takes 9oz of PAG46 oil, and I'm not sure how much (if any) to put back in. It did lose some oil when the accumulator was removed, and not sure how much but it didn't seem like 9oz... Should I try draining all of the oil from the system? Should I use one of the R134's with some oil in it, or could it not be compatible with what's in this old of a system? And I've heard to avoid any kind of stopleak because it can cause problems. Is that right?

Other than the few days it was apart during the HC replacement in the dead of winter, all components have been together, so hopefully that won't have caused any problems. I have the manifold kit and pump to check for vacuum leaks and to pull out any humidity.

Any suggestions welcome. Is there anything I'm missing?
Thanks, Bryan

 

[crunchie_frog]

I have always just replaced the oil in the component(s) that was (were) replaced. I am guessing you are replacing your accumulator, if not I would suggest this since the desiccant in the accumulator absorbs moisture in the air when open (and refrigerant system when closed) and if it was open to the air for several days it may no longer have active desiccant. I would google search for how much the oil the accumulator is supposed to hold, my memory is 3 to 4 ounces. Whatever your search reveals, I would add the oil directly to the accumulator and connect everything back up and pull vacuum and check for leaks and recharge with the correct amount of refrigerant.

 

[bryansr]

I had the accumulator out for a couple days when outside temps were in the 20's & 30's, and it was that cold in my garage. Could enough moisture really have gotten in to affect it? Can you pour the oil into either of the tubes, or does it go into the Shrader valve? Thanks

 

[crunchie_frog]

Your call on the accumulator, I would still replace it myself, especially if it was the original one. I think Rock Auto has them for around $20. You can pour the oil in either tube.

 

[bryansr]

So, I have a new accumulator, and would like to get my AC working this weekend, but a little confused on exactly what I should do. As mentioned, I had to remove the accumulator and heater box on the firewall to replace the heater core, and when doing so lost some oil from the lines and what would have been in the accumulator itself. No other AC components were removed, but I'm not sure how much oil to add. in one place I see the accumulator takes 1oz, another it says 3oz. Is it better to have too much oil or too little? Should I flush the system?

My plan is to:
1) add the necessary amount of oil (w/leak detector) to the accumulator and install with a new expansion valve & o-rings
2) pull a vacuum on the system to remove any moisture and check for leaks
3) if it holds a vacuum, then add the freon.....


Thanks,
Bryan

 

[ranger7ltr]

If it were my system I would flush the condenser, the evaporator and the lines...Also change the orifice tube as it is a filter for the a/c system...Place half the oil in the condenser, half the oil in the accumulator, new of course..Replace all the orings in the system and use Nylog on the connections...

If you have your own vacuum pump and have changed the pump oil in the last 3 months and the pump has been sealed you're golden... If not change the pump oil before trying to pull a vacuum on the system...Air and moisture in the pump oil is just as bad as air and moisture in the condenser or accumulator...Fortunately most newer compressors do not hold oil so that is one concern to not worry with...

Hook up your gauges on the low and high sides and the vacuum pump to the gauge manifold and turn it on before opening the valves on the gauge set...This will purge any air inside the manifold that doesn't need to be exposed to the clean and about to be vacuumed down system... Then open both sides and let the pump run for about 15-20 mins and then close the gauge valves with the pump still on... Close the valves tight as you are watching the gauges for any movement which would show a leak in the system and more work needed to fix it...If the gauges do not move for 10 mins or so, turn the pump back on and reopen the gauge valves and run the pump for 45 mins or so...This will get any moisture in the system out and you will then have as clean and dry an a/c system as you can get...

When your system is clean and dry, you can close the gauge valves again and attach the charging line to your manifold...You should know the amount of refrigerant needed[ just like the proper amount of oil] to charge the system and you don't want to over or under charge it...Attaching the charge line with the vacuum pump attached still also purges any air and moisture out of it to ensure the driest refrigerant charge possible...As long as the system is not turning you can charge into either low or high side but I would recommend charging only into the low side at the accumulator if you manage to charge liquid instead of gas...When you have the proper amount of refrigerant installed in the system turn off your charge line valve and monitor the high side gauge for proper heat transfer... You are looking for 2.3-2.7 times Ambient temp as a pressure on the high side of a properly running system... This can also tell you if the fan clutch is working correctly and if the charge amount is correct..

Your vent temps should be around 36-38 F with the windows up and recirc on or this is what my Explorer runs center vent wise...

 

[bryansr]

When the lines are removed from the rear of the compressor, will much oil leak from it? If so, does the compressor need to be removed and tilted to add oil back into it?

 

[ranger7ltr]

Not much if any refrigerant oil will come out of the lines on the compressor as the compressor does not store any oil in it...The refrigerant oil is concentrated in two main spots; the condenser and the accumulator...Since your system is open pour the oil into the condenser and the accumulator seal the system and pull a deep vacuum on it to remove any air and moisture that finds its way into the open system...

 

[bryansr]

I've taken every connection loose and flushed everything (but the compressor), installed the new accumulator w/ 50% of the oil and put the other 50% in the condenser, and replaced every o-ring using nylog. Pulled a vacuum for just over an hour, closed the gauges at the manifold and turned the pump off, and after 30 minutes the vacuum dropped from 28/29"hg to 25/26. I was planning on putting plain R134 back into it, but do have an extra can of R134 w/stop leak I could put in, but my concern is it also has 3oz of "synthetic oil". Will it hurt to have an extra 3oz of oil in the system? And if not, will it be alright to mix synthetic oil with the new PAG46 I put in? Thanks, Bryan

 

[ranger7ltr]

The leak is probably coming from the o-rings in the compressor.. Not the little o-rings in the back at the hoses... The body o-rings and or the front seal around the shaft... I have never used refrigerant with stop leak but the oil is similar to the synthetic oil you commonly find on the market...I would be concerned about too much oil in the system not for an overfill condition but for too much oil circulating in the refrigerant stream inhibiting the heat transfer through the condenser and evaporator...I also hope you are not getting leakage from the evaporator body...

 

[bryansr]

Well, after 2 months it looks like I'm almost done with my flush and fill. It turned out I was losing vacuum yesterday due to leaking manifold lines where the o-rings on the connections were chewed up. Repaired that and pulled vacuum for another 1.5 hrs tonight, closed the manifold valves, and after 45 minutes it had not lost any vacuum. It takes 30 oz of refrigerant, and I got 24 into it tonight before it got dark and will top it off later this week. I do have cold air from the vents, but I'm still keeping my fingers crossed that I didn't screw something up or that a component doesn't go out after the system being uncharged for 6 months.

A big thanks to crunchie_frog & ranger7ltr for your advice!!

Bryan