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Uniblurb 06-08-2013 09:14 AM

New compressor & AC system questions
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On my 96 4.0 about 3 years ago I bought a new NAPA Cold Power AC compressor and it started leaking 134a out of the front seal 1-month out of warranty. Also installed a new accumulator (filter/drier) and had a shop evacuate the system along with charging it.

So I just bought another new AC compressor which is a Denso (471-0109,, $194) along w/another new accumulator (Denso) since it just started leaking out of one of the hose connections. Also bought an 8oz bottle of "Super PAG 100" oil.

So where I'm getting confused is how much oil to add to the system? And is the oil in the compressor itself separate than the amount of oil in the whole system?

As can be seen in the below install diagram it says to drain the oil out of the old compressor, measure it, then dump the oil out of the new compressor, and put the same amount in that was in the old compressor. I don't trust the old compressor oil level (not OE) because of leaks in the system where I recharged it but didn't always add more oil.

The spec for the whole AC system is 7.75oz oil and the new bottle of PAG 100 oil says to not mix with other oils. I'm going to use my flush tank/kit for flushing out the evaporator (replaced 1 1/2 years ago), the other lines, and the condenser so there should be no oil left in the system. Should I just discard the new compressor oil and add exactly 7.75oz from the new bottle to the compressor? Or maybe I should pour it in the suction line of my manifold gauge set which I've seen done before?

Thanks for any help/advice! Also wondering what brand/type of 134a I should add since there's so many out there? Was thinking about going with the "Arctic Freeze" but maybe just the auto store brands would be fine? Know the "Refrigerant Charge Capacity" is listed as 1.75 lbs, which would be 28oz total, but don't know if this includes the oil?

Thanks again!

Uniblurb 06-09-2013 05:44 AM

Bump. Any help/input on this one? My wife has taken over my ZJ as her dd to/from work and I really need to fix the AC since she's bringing home the wrath of sitting in hot rush hour traffic! Lol and thanks.

coralman 06-09-2013 08:52 AM

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I,ve never used one of the flush kits before so I don't know about them. Seems like I read some mumblings about them but to have a warranty they require you do. Factory system is empty when it comes off the line . "All components are oil free except the compressor. When the system is charged oil distributes to the other components." Thats from a 98 fsm. The comp maker assumes probaly that you are replacing the accumalator and adds the required amount when they oil charge it. But like you I wouldn't trust it. Here is the chart from the fsm.

Attachment 635956

I would imagine its hard to get it exact unless you build the system from scratch. Also, I wonder if the flush kits I've seen have enough propellant to push the cleaner/oil outof the components. I don't like the idea of the remnants of that stuff roaming around in the system. If It was me, and this adds expense unless you have access to a/c tools, I would blow the stuff out with a regulated dry nitrogen tank. Crank the regulator down about half way and see what the flow is. You don't want it too high or you might create leaks. Also if you are going to flush,I would spring for a new orifice tube as well.

Using the chart you may be able to do backwards math and get close. Hope this helps.

Uniblurb 06-09-2013 12:02 PM

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Thanks for the input coralman, appreciate it. Actually the flush kit I bought 3 years ago works well and still have half the pricey solvent left. I connect the tank right to my air compressor and can put 100psi through the open-ended cooling system if I want. Doesn't seem to leave any oil/residue when done.

Good point on replacing the orifice tube since I'm replacing the discharge line/hose anyhow. So actually only the evaporator and condenser would be left to flush out.

The spec for the "AC Refrigerant Oil Capacity" is just slightly higher on the 96 where it's 7.75oz total. The FSM also says if you replace the accumulator you should add 4oz of oil to it. This I don't understand since once the system has been opened up it needs to be evacuated with a vacuum pump which will suck the new oil right back out.

So if the total refrigerant charge capacity is 28oz total, and I add 7.75oz of oil, then I would assume only 20.5oz of 134a is needed for a full charge? I'll go by the manifold gauges to get it close as possible.

I'm going to have to figure out how to add most of the can of oil to the evacuated system w/o letting the air/humidity in. Wish it was in an aerosol/pressurized can.

Thanks again.

coralman 06-09-2013 12:29 PM

I think oil capacity and refrigerant capacity are two different things, not to be added or subtracted from one another. I think that you can pull your vacumn and use it to pull in the oil charge for the accumalator at the low side charge port since you will already have the oil in the compressor. It will brake the vacumn but that shouldn't be a problem as long as you keep the hose submerged in the oil. There was a video that showed step by step how to but I can't remember where I saw it. Once you give a little settle time you should be able to repull your vacumn without sucking out the oil.

a70eliminator 06-09-2013 12:35 PM

Add the oil to the system, divide the 7.5 oz whatever it tells you some in the compressor, some in the reciever, the oil will not be "sucked" back out by the vac. pump, it will just lay there, only the moisture will boiled off along with the non-condensables, pump the system down to less than 200 microns weigh in the 28oz of 134 and your done, the refrigerant will pick up the oil and evenly distribute it throughout the entire system.
Coralman you are correct.

Uniblurb 06-09-2013 07:09 PM

Thanks for the help guys. Never knew the oil will stay in the system when evacuating and makes more sense now. Also nice to know the 7.75 oz of oil is not included in 28oz charge of 134. Sounds easy enough and thanks again!

Uniblurb 06-15-2013 05:04 PM

Well I installed the new compressor, accumulator, liquid/orifice line and discharge line late yesterday. Flushed the evaporator and condenser before hand then blew air through them. Evacuated the system with a vacuum pump running about 45 min with new parts installed and even though I had some line problems it stayed the same overnight so would assume no leaks.

So charged the system early today and did have some problems. Have no idea why when I removed the sealed suction line (yellow/middle) on the manifold gauges it from the vacuum pump and connected it directly to a 12oz can of 134/valve it took almost 20 min to get it in the system on the low port? I did try the trick of putting the 134 can in a pan of hot water and the 2nd 12oz can went in much quicker. The clutch started kicking on/off at the beginning of the 2nd can.

Since an empty system calls for 28oz of 134, and had already put in 24oz (2 cans), went ahead and tried to put in about 1/3 of a can but may have put in half. I was hoping I could get it exact but I'll be darned if the manifold gauge readings made any sense to me.

So right now the clutch will not kick off, runs constantly, and hope I don't damage it. Thought maybe it was the new pressure switch on the Denso accumulator so I took my old one off put it on and made no difference. Then I switched the horn relay with the ac clutch relay and the compressor still runs constantly.

With the valves closed on the manifold gauges the low side reads 48psi, doesn't move, and the high side is reading 200psi and also doesn't change. With valve open both the low and high side reads 120psi.

So do others think I overcharged the system and maybe that's why the clutch won't kick off? I've heard you need to let the system settle some but I've been getting the same readings all day. Can I bleed any of the 134 out of the system if I have a couple oz too much in?

Thanks for any help and kind of in a bind right now with it getting dark/ready to rain!

Candymancan 06-15-2013 05:18 PM

Just go to the autoparts store and get those gauges that tell you the charge.... and charge the thing per what the temperature is outside... They sell kits with the gauge that has a temp/charge thingy on it with an arrow.. They always work for me.. If its like 90f then i put almost 45-50psi in the system.. and that usually holds for a few months before i gatta refill it again.. I have a small leak in both the 5.9 and the 4.0 it isnt big enough for me to care i just buy the bottles and refill lol. Run the A/C with the recirculate button on and let it run for 5 minutes full blast and with it still running check the low side pressure... it shouldnt be anymore then 45-50psi believe. That is more then enough to keep it cool with the temps in the 90-100f range

Btw when the system is full the clutch will run pretty much non stop when idling, when the clutch turns off and on and off and on thats when its low on refrigerant... One you step on the gas and the rpms go up it should turn itself off and on

Mickey_D 06-15-2013 05:30 PM

Just for future reference, if you have to evacuate the whole system again, try using this stuff to charge it back up.

Less head pressure means the compressor has to do less work, which means better fuel economy out of the Jeep when the A/C is running. It's also half the damned price of store bought freon.

Candymancan 06-15-2013 05:36 PM

Im not too great with a/c system, but wouldnt less pressure mean it wont cool as good.. Specially in warmer temps.. thats why you have to fill it up per what the outside temp is

Mickey_D 06-15-2013 05:41 PM

R12 runs at a much lower pressure than R22, which runs at a lower pressure than R134a. All for the same cooling ability. Hell, some of the larger industrial applications where they run water down the condenser only run at 10-15psi.

ghiotom 06-15-2013 05:48 PM

Try revving the engine to 1500 rpm or test drive it. I'll bet it will cycle then. If the temps are pretty warm and you're idling, it probably won't cycle. I don't think you're overcharged, the gauge hoses will hold 2-4 ounces from what I've read.

Uniblurb 06-15-2013 06:26 PM

Thanks for all the input guys and never thought about giving it more rpm to see if the clutch stops! System calls for 28oz of 134 when empty and maybe I did put closer to 30oz in it. But nice to know I might have a couple oz in the hoses then it would be right on.

I've used the gauges on the fill cans before (have one) but got in the habit of also using a set of loaner manifold gauges from a local autoparts store. Don't know why I had no problems with there's but trouble reading my new ones. Was shooting for 240psi spec on the high side, rather than 200psi, since 80 degrees but would have it overfilled if I put that much in.

My 93 4.0 XJ, which uses R12, just started leaking a couple months ago and that Enviro-safe master recharge kit for $25 sure looks inviting. Heck just bought a fitting R12-134a conversion kit (unopened) for $12 and I put $40 of of Advance 134a in mine and can't use a discount code on that stuff.

Thanks again for the input on mine and feel more at ease now. ;)

a70eliminator 06-15-2013 07:06 PM

I would expect to see high side pressure just sitting there ideling at least 250-300 I would mist the condenser with a cool water from a hose to keep the pressure down, sounds a little low yet @ 200psi head.

FYI on your manifold set, never open both valves, you open the low side valve to introduce refrigerant from the center yellow hose, or you open the high side to pump refrigerant into a recover cylinder, but never open both, unless your just pulling vacuum on the system.
When you go to remove from the system, first disconnect the high side at the quick coupler, then open high side manifold valve, slowly open the low side valve and the high side pressure will be drawn down and refrigerant introduced into the low slow side, this will minimize loss through the hoses.

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