boomyal wrote:

unless it is a two stage pump, you are not likely to get any more.  The key is, will your system hold the 20 inches?  If it does, that would probably be sufficient.

Thanks Boom,  ijts a single stage pump.   I also didn't check to see if it was calilbrated accurately either.  I will turn both guages to the closed position, turn off the pump.  and see if it holds at 20 for leaks.

I am not an expert but, the Harbor Freight single stage vacuum pump worked for me. The problem is that you need a micron gauge to get more accurate readings. You should be a able to pull 500 microns vacuum to make sure all of the moisture and contanimates are out of the system. Look at this chart and you will see what I mean. Your system is contaminated or you have a leak.


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From what I know, if you can't pull a 500 micron vacuum you haven't removed all the moisture from the system. The readings on the manifold gauge are so vague that you really can't tell how much vacuum you are really pulling. From the chart; 29 inches of vacuum could be 25,400 microns or 29.5 inches could be 12,700 inches. Using a purge of dry Nitrogen would help remove the contaminants and moisture. Again I am no expert, but when I do my AC systems I use a micron gauge and nitrogen. I got my procedure from some of the EPA Certification study guides.

You really need to do two tests: a leak test by charging the system with dry Nitrogen to about 150psi. If it holds pressure then you have no leaks. The next test is the vacuum test to make sure you've got all the non-condensibles out of the system by getting to a certain micron level of vacuum. This vacuum process is not a good leak test. The Nitrogen leak test purges some of the non-condensibles out while the vacuum leak test will pull them in and contaminate the system more(if you have a leak). The micron gauge has a very precise reading.and is supposed to be used to make sure the system has all the non-condensibles removed. A regular refrigeration manifold vacuum gauge is not accurate enough for this porpose. I'm just say'in.

MustangSteve wrote:

My new MURRAY AC gauge set, when hooked up to my system, showed the vacuum was going down to about 22" hg.  Tapping on the gauge with my fingernail got it to go immediately to 29".  That said, you may be dealing more with gauge inacurracy than pump incapability.

Let it pump a couple of hours, then let it sit overnight.  If it holds, you should be good to go.

 MS -  Well, i did let it pump a couple of hours, but i didn't let it sit overnight. I let it sit for a couple more  hours and it stayed on 20 so i figured I was good to go. I figured that 1.5cfm pump couldn't do 29hg like boomyal says.  I only had the tools that autozone had available for rent.  It was a slow charging process, but it did finally take 1 small can of pag oil/refrigerant, and two 12 ounce cans of R134A.  At first, the clutch wasn't engaging at all with the first can of pag oil/refridgerant, with the 1st full can of freon then it would go on and off.  Eventually after the first full can of freon the compressor clutch stayed on. Last night the low side was around 35, and the high side was at 125. Both were steady readings with the clutch engaged all the time. I have a 3rd can but I didn't put it in since I thought these were the right readings to achieve and didn't want to overfil it. I also looked for the hoses to be cold and wet and they weren't. Only the drier had some condensation on it, and some of the line with the orifice.  I didn't check vent temps with a gauge, but i put my hand over the vents and it was cold. If anything I might put in one more small can of pag oil/ refridgerant.  I will take it for a test drive today. Just to make note: i replaced all the  hoses, the drier, and all the O rings on all the snap lock connections to the newer green ones, and the o rings on the compressor, and installed new r134 converter fittings, and poured pag oil in the compressor and the condensor and the evaporator before snapping them all together. IF i have a leak, then its either the condensor or evaporator, which will both have to wait to get replaced if they are bad.

KeithP - I appreciate the info, but I didn't know about the nitrogen test or the micron gauge before.

  Getting it ready for bash trip.  I might pick up a power steering pump today too and make that next weekends project. 

Now the ac in my wifes 2005 kia sedona van isn't working. the compessor clutch is not coming on. Probably needs a compressor. thats not a job i can handle. extremely hard to get to it from underneath.

MustangSteve wrote:

Don't over-oil it.  It doesn't take much to lube the system.

The acid test is this...  Does it blow cold air?  In the end, that is all you really care about.

In the old days, when freon R-12 was $0.99 per can, and I did not have a vacuum pump, I would introduce a can of freon into the system, then hold the high pressure port open while running to expel as much air/freon mixture from the system as possible.  (Basically using the compressor as a big vacuum pump).  That got the sytem holding maybe 10% freon and 90% air.  Then same with another can to get 80% air and 20% freon.  Can after can went in with same procedure until it started blowing cold air, until I had gone through about 12 cans.  And, guess what !!!  It blew cold air.  That hole in the ozone was not ALL caused by me...  We never even heard of global warming back then, except in the summertime.

According to Al Gore, the Global Warming issue and Ozone depletion problem did originate in Texas and somewhere around the Carrolton area. LOL

Oh man...stand back.

Mark,
Don't know where you are at with this by now but don't over think this thing. If you have 22 on it and the pump keeps it there for hours charge it and call it done. The new drier will more than likely take care of the rest. For future reference and good leak detection metheod is to charge it with a small amount of refrigerant and pressurize it with nitrogen and use an electronic leak detector to check for leaks.