As for oil absorbing water, I don't think most oils are hygroscopic (i.e. attrace moisture) the way brake fluid will. I would imagine you could look this up or consult the manufacturers. How long has it been exposed to air? Hours or days? It might be something to worry about. As for the oil in the accumulator, I can't remember if that would matter or not. I'd err on the side of consulting with the manufacturer of your compressor.

 

fortunately, i only opened the compressor today, so not long on exposure. accumulator was only opened briefly to add the oil, then installed on the evap and capped off at the compressor end, but it's been almost 24 hours since i did that.

you would call manufacturer regarding oil and moisture or regarding any mixing of different oils?

 

Regarding PAG oil and moisture:

"PAG oils are by nature hygroscopic. That means they quickly absorb moisture.

The testers examined the containers of five different manufacturers as well as a simple glass container (Erlenmeyer flask) serving as a neutral reference. All containers were filled with the same amount of the same PAG.

In four of the five containers the moisture content in the oil was above the maximum permissible limit (800 ppm in our test) already after three days.

PAG oil literally attracts water. A leaky closure or an unsuitable container material is enough to let the PAG oil absorb moisture from the ambient air. So called vapour-tight containers are used to avoid this effect.

If refrigerant, oil and water react with one another, this can lead to the formation of acids or slurries. Acids damage the components of the A/C system and cause problems in the refrigerant circuit, e.g. corrosion of the compressor. These reactions occur significantly more quickly if the system contains more than 800 ppm of water."

I do not know if this is a problem in your case, I just know that the conventional wisdom is to close everything up quickly because PAG oil,is actually like brake fluid. I wish I could be more specific for you.

Regarding mixing oils, that's another worm hole. You will read everything from no issue if they are "equivalent" to don't do it the additives do not play well together. Most sources will say that its ok if only trace amounts are left behind unless its a mineral oil conversion with R12.


George

 

ok i'm going to risk it on both counts.

keeping what's already in the accumulator and going top it off to 4 oz. of blue pag. subtract 4 oz (plus .25 oz of leak detector dye) from what i just drained from compressor and add that remaining volume of blue pag to the compressor, close it up, hand cycle through, and start the evac. I don't have nitrogen to test the seal, so I'm just going to skip to sucking it down. I know it's not the best way, but I feel like it's better than nothing.

 

The dry nitrogen pressure test just saves time. If you hold the vacuum after the evac, thats just as good. Its just a pita if you failed to hold after a one hour or more vacuum plus 30 min wait only to find that you have to fix a leak and then start over. A shop cant tolerate that type of rework. Also, dry nitrogen helps you get a wet system dry faster. You evacuate, nitrogen purge and repeat until you hold. That can take a lot of time out of an evac cycle.

Hope it works out.


George

 

Increase your evac time to at least an hour, longer if you have the time. When the system is in vacuum the liquid moisture boils into vapor for removal. Moisture in the oil takes longer to come out. Don't go under 200 microns if you have a micron gauge. Most consumer pumps and low grade hoses wont go that low.


George

 

I think George has a good handle on this.

Whatever you do, you'll be glad you did it right the first time.

 

Ok, so I have everything installed and sealed, vac pump is running for the seal check first. If everything is fine with that, I will pull a vac on it for a few hours.

At this stage, if it does not hold the vacuum, how do I know where the culprit is, other than retightening everything? I don't have any crowfoot sockets, so I can't really use the torque wrench for anything other than the hose manifold coming up to the compressor.

How close do I need to get to -30 mmHG? Is anything below -20 ok?

 

The reason why professionals use a micron gauge is because a vacuum indicating a clean and leak free system is around 500 microns and the difference between that and a system that is still not dry is impossible to resolve on your manifold gauge set. A perfect vacuum is 29.92 inches of mercury vacuum and so if the gauge set is all that you have the conventional guidance is to get the vacuum reading somewhere between 28-30 in hg reading and run the pump for a couple of hours in your case. You should pump down everything up to the ports by closing the port connections and make sure that your pump and gauges/hoses are capable of this first. Then make sure that holds before opening the ports and pulling down the system. Evacuate from both ports its faster. The pump should have new oil in it. If you do not perform this check first you might chase your tail on a hook up leak or permeating hoses, etc.

The reason for the nitrogen test is because if you fail the vacuum process (especially without a micron gauge) its hard to tell if its moisture vs a leak or to find the leak. You would have to pressurize and look for the leak or just keep running the pump to see if the vacuum develops as moisture is removed.


George

 

So when I closed the valves on the manifold to see if the system would hold vacuum, it was losing it pretty quickly. My suspicion was the bolt holding down the hoses, so I set the torque wrench to 25 ft-lbs and it never clicked but I cracked the aluminum block on the hose set, so I guess my torque wrench is garbage.

I capped the hoses and replugged the compressor.

Did I just completely ruin everything or do I still have a chance/time to resolve the issue and avoid the issues we were discussing above if I get a new set of hoses soon enough?