AC advice needed

I was going to rebuild my AC so I ordered an o-ring kit and accumulator. I also got a vacuum pump, flush kit and manifold gauges from Autozone.

The compressor was unplugged when I got the XJ so I assumed it might be bad. Last night I hooked up the manifold gauges and there was no pressure in the system witht he engine off. I was pretty sure it was empty so I ran the vacuum pump and drew a vacuum on the system. I let it sit for a few hours and it holds the vacuum at -28.

I then plugged the compressor in and jumped the low pressure switch. The compressor runs without making any nasty noises or anything so at least it isn't locked up.

My question is, should I just fill it with freon and send the new parts back or if you were me would you go ahead and replace the accumulator, change the o-rings and flush the system before putting freon in it?

Im pretty new to AC systems but Im trying to learn quick.

If everything seems to be working and no leaks I would just re-fill it with the freon and some of the dye so if it starts leaking later you can see it.

How do I know when it is full. Should I just estimate bsed on the label on the shroud and the fact that each can is 12oz by weight?

rshackleford said:

I was going to rebuild my AC so I ordered an o-ring kit and accumulator. I also got a vacuum pump, flush kit and manifold gauges from Autozone.

The compressor was unplugged when I got the XJ so I assumed it might be bad. Last night I hooked up the manifold gauges and there was no pressure in the system witht he engine off. I was pretty sure it was empty so I ran the vacuum pump and drew a vacuum on the system. I let it sit for a few hours and it holds the vacuum at -28.

I then plugged the compressor in and jumped the low pressure switch. The compressor runs without making any nasty noises or anything so at least it isn't locked up.

My question is, should I just fill it with freon and send the new parts back or if you were me would you go ahead and replace the accumulator, change the o-rings and flush the system before putting freon in it?

Im pretty new to AC systems but Im trying to learn quick.

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-28 is not low enough. You have a leak, somewhere. Check the test gauge assy hose connections first, since you a re nebie to AC, make sure the test hose connections are not leaking. -28" is not a huge leak, but is large enough to loose an entire refrigerant charge in hours to one day. It should reach -30" very quickly, and with the compressor off, and valve closed, it should hold -30" for hours with no change.

Hoses on the AC system can leak, quick connect fitting o'rings can leak, the evaporator or condenser connections can leak, and the expansion valve seals (on the bottom) can leak.

What year is it? Freon has not been used since the early 90's. Most are using R-134a refrigerant now.

Its a '99. I meant R-134a refrigerant, not Freon.

Ill tightent all the hoses and see if I can get down to -30. If I can't get down to -30 should I just put some R-134 with dye in it to try and find the leak or should I just tear it apart and replace all the seals, quick connect fittings, etc...?

rshackleford said:

Its a '99. I meant R-134a refrigerant, not Freon.

Ill tightent all the hoses and see if I can get down to -30. If I can't get down to -30 should I just put some R-134 with dye in it to try and find the leak or should I just tear it apart and replace all the seals, quick connect fittings, etc...?

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First see if it will reach and hold -30" of vacuum. I have had an ever so slightly, not quite tight enough gauge hose connection leak enough to make me think I had a leak.

Being 12 years old it may need new seals. But the o'rings when they dry out, from the ac not being used for 6 months to a year or more, do not seal well on the newer R-134-a systems. The oil/refrigerant when cycled gets to the o'rings, and makes them swell a little and helps them seal, and keep their old round shape better. If it does not seal completely, I would have a local shop add a little R-134-a, and then have them test with an electronic tester to find all the leak locations. Then do the work yourself.

I have had slow, but bad enough leaks at the compressor shaft seal up front, at the expansion valve o'ring seal on the bottom of the valve at the firewall (neither o'ring is replaceable) and at the hose crimp connections (not repairable), and with R-134-a at any and all of the o'ring sealing points like the tubing quick connects.

Lastly, you want to make sure the evaporator does not have a hole in it. I hear that the newer ones (aluminum) are not nearly as hardy as the old ones (Thick copper) from the 80's and older. I have heard that road salt areas of the country eat them up !!!! So have them test for R-134-a inside the cab as well! I have tried to short cut this process and waisted time and R-134-a too many times.

If you can hold -30" of vacuum for 6 hours, on the low and the high side, the only thing that can get you is a bad expansion valve (does not open or close), bad compressor, a blocked hose (bad on the inside) or a plugged dryer/filter.

Once you have any leaks fixed, and any parts replaced, you need to open the system and replaced the filter/dryer!!!!!! Do not do that too soon, and do not skip that step!

The dryer removes water and small particles that corrode the internals, damage the oil, and plug the expansion valve. If you replace the dryer too soon, and it gets exposed directly to humid air for a day or more, it needs to be replaced!!! They are not expensive.

When I start having problems with an old Auto AC, I usually replace all the rubber hoses, and seals, and the expansion valve and dryer. And the compressor if it leaks. You can find some great buys for parts on Ebay!!!! I have found new compressors for under $100 on ebay.

You can also find great help and parts at www.ackits.com
They have an excellent AC troubleshooting forum!!! And they have any part you might need!

I wasn't able to get below -28.5. Although, I left the guages on it and it has bbeen at 28.5 since saturday evening. So it doesn't seem to have a leak. I read in other forums that altitude affects the ability to get down to -30 and that for each 1000' above sealevel you loose about 1 in Hg.

Do you have any insight regarding the fact that Ic an hold -28.5 for 36 hrs? and or the affect altitude has on pressure?

thanks

rshackleford said:

I wasn't able to get below -28.5. Although, I left the gauges on it and it has been at 28.5 since saturday evening. So it doesn't seem to have a leak. I read in other forums that altitude affects the ability to get down to -30 and that for each 1000' above sealevel you loose about 1 in Hg.

Do you have any insight regarding the fact that Ic an hold -28.5 for 36 hrs? and or the affect altitude has on pressure?

thanks

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LOL, I am at sea level, have been for 55 years. What is your altitude? I am not sure what the correction factor is, but the guys at ACKITS.org will known for sure. If it held for 2 days, it is pretty well sealed, a good sign.

Since your system has lost all it's all it charge, you can be sure it probably has an operating leak somewhere, like a front shaft seal on the compressor, or seal on the expansion valve. So do not fill it all the way. Put in just enough to get the compressor to run, and to find the leaks. You can use a fluorescent dye and UV light or go to a shop and let them locate the leaks with an electronic tester, which are ultra sensitive. They find slow leaks the dyes miss!!!! Ask me how I know!!!!!

My last nightmare, was a compressor leak on the front seal, that held vacuum, but leaked under pressure while rotating. Even the dye did not find it, but the electronic tester did. Choice is yours. I filled many a system, that had 1 can per year leaks, with out fancy leak testing. But loosing $40 worth of R-134-a in multiple guess trials, is no fun.

You might try a 12 oz can, to make sure it runs first, testing the switches, and valves and thermostat / expansion valve.

Thanks man thats very helpful.

I have a couple more questions. If I just put one can in and am able to track the leak down what is the best DIY way to get that refrigerant out of the system and the system completely empty so I ultimately can get close to the proper weight on R-134 in the system.

I seem to keep coming back to this point when I work through the process in my head. If I don't know how much refrig is in the system how do I know when it is full?

If it is holding vacume it dosn't have a big leak, so you are ready to charge. You really need a mahine or an accurate scale to get the correct amount in and if you do find a operating leak, the only way to get it out without a machine is to vent it.

If you find a leak worth bother to fix, after adding one can, it is usually gone, leaked out in a few days on its own, LOL, before you get around to fixing the leak, LOL.

Only way to fix a leak is to open the system to replace the leaking part. No refrigerant remains after opening the system to fix a leak, if there was any left.

I never used anything but a set of gauges and known ambient temp, and evaporator temperatures, and premeasured cans to add the right amount of refrigerant. Check the FSM for the proper fill amount. Or ask the guys at ACKITS.com, they have that data. Never used a scale in 35 years to measure additions, or fills in automotive. Yours should be between roughly 18 and 28 OZ IIRC, but not sure of the year, and the exact fill.

Ecomike,
Great help. Ive been over at ackits.com and I must of gotten off on the wrong foot because the only answer I can get is "there is no way to get the proper amount of refrigerant in the system without having professional equipment and scales available at a shop". So they are contradicting you.

It still has -28.5 inHg of vacuum after 4.5 days. Im pretty sure you are dead on with the operating leak. Im going to follow your advice and put just enough refrig, with dye, in the system to get the compressor to run and see if I can find the leak.

I bought the XJ jst a couple months ago and the compressor was unplugged when I got it. I suspected the compressor was locked up since it was unplugged but it ran fine. Im not sure why they would have unplugged it for just a leak but who knows.

thanks again for all the advice. It is very helpful.

Im preparing to build the XJ for off road but I usually drive to the events rather than trailer and the wife needs her airconditioning Besides, AC is one of the few mechanical areaas I haven't tackled so I saw it as a challenge. I suspect Im like most other people here, working on our jeeps is almost as much fun as driving them.

It is not necessary to get the exact fill on the AC. At the proper fill (+/- 1-2 oz) the high and low side pressures will depend on the ambient temperature, altitude and humidity, and the dash settings for the blower and AC.

Main thing is to get about 45-50 F air at the inside vent (use a temp probe, dial gauge), with AC on Max AC and blower on normal, and no more than 225 psi on the high side gauge on a hot day of about 90-100 F with AC on normal, blower on high. Low side readings should run between 25-40 psi. If low side drops below 25, there is not enough refrigerant, or some other problem. If high side gets over 225, or low side gets over 40 psi, there is too much refrigerant or a mechanical problem. These are at sea level, so you may need to adjust some for altitude!!!

Did you give them your year, make and model and ask what the proper fill amount is?

Ecomike said:

It is not necessary to get the exact fill on the AC. At the proper fill (+/- 1-2 oz) the high and low side pressures will depend on the ambient temperature, altitude and humidity, and the dash settings for the blower and AC.

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Boy, that statement is in direct contradiction with the guys at ackits.com. They insist that they EXACT amount of refrigerant is critical and the system will not work and I might even destroy the compressor with even an oz too much or too little.

Ecomike said:

Main thing is to get about 45-50 F air at the inside vent (use a temp probe, dial gauge), with AC on Max AC and blower on normal, and no more than 225 psi on the high side gauge on a hot day of about 90-100 F with AC on normal, blower on high. Low side readings should run between 25-40 psi. If low side drops below 25, there is not enough refrigerant, or some other problem. If high side gets over 225, or low side gets over 40 psi, there is too much refrigerant or a mechanical problem. These are at sea level, so you may need to adjust some for altitude!!!

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Adjust up or down for altitude? I assume down.

Ecomike said:

Did you give them your year, make and model and ask what the proper fill amount is?

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I actually have two vehicles I am working on AC issues with at the same time. I have a WJ that I pulled a vacuum on and then over charged. I asked ackits how to get the proper charge. Since I generally am trying to learn more about AC systems and the questions span both vehicles so
the questions ultimately apply to both vehicles.

Ill just check the sticker under the hood once Im ready to fill it for good.

If you have a vehicle with a working AC, you could test it for gauge pressures and use it as a guide.

The gauges read what is called gauge pressure. Gauge pressure is actually a differential pressure, measurement of the internal pressure minus the ambient pressure due to the weight of the atmosphere (5 miles of air under gravity acting on the gauge). So the same factory fill might show a higher gauge pressure at higher altitude, than at sea level.

Would need to convert 1.5" of Hg to PSIG (pounds per Square Inch of Gauge Pressure).

http://www.unitconversion.org/unit_converter/pressure.html

28.5 .... is 13.98 psig (usually listed as PSI)

30" Hg is 14.69 psig, so it is only a 0.71 PSIG difference, if I did that right. Also known as insignificant, LOL.

But there are other larger issues, like humidity and ambient temperature, and how how the thinner air at higher altitude has less density, and therefore cools faster (lower mass heat capacity per cubic foot of air volume) that also affect the normal max/min gauge pressures at various altitudes.

Just shoot for 25-40 psi range on the low side, and 175-225 psi on the high side as bounders, limits not to be crossed, for all AC settings, hot days with high humidity for mas pressures, and low pressures for the cool days, testing blower on high, low, and Max versus normal AC settings, and you will be just fine. That is how the engineers determined the proper fill for the specs, the weights and measure guys are so proud of! LOL

Mine holds about 50-75% more than the newer systems. Mine are late 80's models, so +/-1 oz, or even 2 oz, is not a big deal. On the 2011 models they are starting to use a new refrigerant from Europe I think where the entire fill is something like 8-10 oz, in which case an extra 1-2 oz is a problem. Mine holds something like 28 oz of R-134-a. +/- 1 oz on mine is only about +/- 3%. Yours may be an 18 oz fill if it is a 200x model? I think early 90's were still about 26-28 oz, but I do not have the exact data. My friends 1995 grand cherokee holds right at two 12 oz cans, net of about 24 oz as I recall from last summer.

I try to do my charging on hot (like 100 F here), humid high load days to make sure I stay under 235 Psi max under worst conditions, and still get about 50-55 F air or Normal AC settings.