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I am going to put in a smart vov in my car. I want to do this myself but I have never done a full charge on an A/C system that has been open. Do you have to pull a vacuum on it, or replace the drier, add oil or what?? Or can you open it for a few minutes and then close it back up and charge it?? I have recharged a system that were a little low, that seemed fairly easy. Can someone give me a step by step on how to do this, I would greatly appreciate it.
94 944, 237,000 miles. Question how do you get the mileage badges?
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The thing is this; if you don't get a vacuum in the system before you charge, the pressures will be wrong because the charge will have air in it. As a result, you won't feel the whole benefit of the VOV, although it will improve the performance somewhat, if it is currently lacking in some form.
The accumulator/dryer tank should be replaced if it is a year or two old, and the system has been opened. You do have to add oil to the system at that point, but it is only a couple of ounces that usually ends up in the accumulator. If you want, you can dump the accumulator tank and see how much oil you get out, and then put that much back in, plus maybe 1/2-1 oz. for residual.
I'd almost recommend not replacing the current orifice tube, or opening the system, if the system is cooling well right now. If you don't think it's cooling well, you might as well do it right.
--
1992 940 wagon, 72k
make people envious; smile often.
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posted by
someone claiming to be rwreagan
on
Mon Jun 3 04:37 CST 2002 [ RELATED]
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FWIW, I've recharged several systems (replaced compressors, converted to R134a, etc.) on my cars over the years by drawing a vacuum using an old refrigerator compressor motor. Have a fitting attached to the input line on the motor-compressor that you can attach the vacuum guage to, and let it run for awhile. Of course, if it's just a one-time job it might be easier to let a shop pull the vacuum for you.
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posted by
someone claiming to be ringlee
on
Mon Jun 3 05:23 CST 2002 [ RELATED]
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Do you have a design for this? Suggested fittings and sources? How do I adapt the compressor to an auto a/c vacuum pump?
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posted by
someone claiming to be rwreagan
on
Mon Jun 3 09:56 CST 2002 [ RELATED]
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Here are links to a couple of pictures of the pump:
http://www.heavenlystrings.com/pump1.jpg
http://www.heavenlystrings.com/pump2.jpg
You can see the fitting soldered onto the intake tube. I found a fitting at an air conditionnig shop that has the same threads as on the top of a can of R134a, so the vacuum guage would fit onto it. The only fitting I could find was a "T" fitting, so bought that and capped the open end. There actually were three tubes coming off the compressor: an intake or suction, an output, and a third that I don't remember what it did. I capped the third, left the output open, and put the fitting on the input (suction) tube.
This will draw a vacuum of around 29.5 inches, making it easy to evacuate and recharge the system.
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posted by
someone claiming to be rwreagan
on
Mon Jun 3 06:18 CST 2002 [ RELATED]
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No design or specs. Mine is decidedly low-tech. I took the motor/compressor (it's one unit) from the refridgerator and attached a power cord. When I ran it, I could tell which tube had the suction (the tubes are rigid metal maybe a quarter inch outside diameter or less. The tubes were cut with wire cutters to get the compressor out). I went to an air conditioning shop to buy a fitting that my vacuum guage center line would fit to (couldn't find the fittings at any auto parts stores), and took everything to a local machine shop to have the fitting soldered onto the suction tube. BTW, this is my second version. The first version had the screw fitting soldered to a copper tube, and the copper tube was attached to the suction line of the compressor with a rubber tube and clamps. It held the vacuum, though.
Now I can attach the center (yellow) hose of the vacuum guage to the fitting on the compressor suction line and attach the blue and red lines to the low and high side ports of the air conditioning system.
Purists will laugh, but it works and is cheap. I'm not sure how my vacuum compares to one from a "real" air conditioner pump, but it registers about 29.5 inches on the vacuum guage. I've replaced maybe six or seven compressors on various cars over the years (including a 240) and charged the systems myself. Costs seem to run around $125 - $220 for a reman compressor, plus $30 - $40 for the Ester oil and R134a. Much cheaper than the shop would charge.
One footnote: the refrigerator compressor motor should have a couple teaspoons of refrigerator compressor oil to ensure it's properly lubricated. So you have to be careful not to pour it out when you're handling the compressor. The oil should be in the compressor when it's removed from the refrigerator, unless the refrigerator has been laying on its side.
Robert
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Robert
I looked at your pictures. My set up is much the same, not very elegant but it sure works. That does look like a rotary type compressor judging by the shape of the containment.
--
David Hunter
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Steve, I have also done this with an old compressor, just sweated on a female flare fitting, inserted a small O ring then attached a male to male flare adapter same thread as the R12 hoses. Bought it all at Lowes plumbing section. Stuck on a plug with cord for power and that was it. I think you will find the suction line is the larger one of the two that you must cut when removing from the fridge, most likely copper 1/4" OD. The other is the high pressure leave it open, it may spirt oil once in a while and the third line will be sealed.
There are 2 types of compressors used in refridgeration, rotary and reciprocal. Having recently experimented a bit I found the rotary draws down to a higher vacume and runs silently. On my rotary compressor I see a good high vacume. I have a cheap guage set so could not swear that it's at 29.5 but another reciprocal unit would only go to about 27 or so. These rotary units are usually used on smaller applications such as small fridges, dehumidfiers. I think most AC units are the reciprocal type. The compressor I have was out of a small wall mounted water cooler that you see everywhere and was manufactured by Aspera. It is only about 6" high, draws only 1.5 amps running. It may take a long time to vacume down a large home AC system but will work fine for car use. If you find one, give me the model # and I may be able to tell you if it is rotary or not. Internal cooling of the compressor may also be an issue as I think some rely on cooling by oil and the freon circulation. The one I have was labled "thermally protected" and I have ran it for hours with a full vacume, it got warm but did not cut out or burn up.
BTW I found a source for R12. A guy in CA who sells over eBay. He will sell immediately no bidding for around $18 for 12oz can. Expensive but cheapest I have found. He will want an EPA Section 609 Certification number.
I am preparing to repair my daughters 240 AC and that is why I have been doing all this research and experimenting recently. I now have several fridge compressors lying about on the garage floor, one cut open and one burned out. It's been an interesting learning project and I have been intending to share this on the Brickboard.
I wish I could be more definite on the types of compressors that will work and then maybe find a source such as some company that scraps water coolers or something. I scrounged 2 compressors from abandoned f idges at the side of the road. Found the water cooler sitting in a corner at one of my customers. These are not exactly reliable sources. Seem to vaguely remember someone here from over a year ago that was involved professionally in commercial refridgeration and AC systems. Was it Tom Irwin maybe?
--
David Hunter
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posted by
someone claiming to be ringlee
on
Mon Jun 3 03:38 CST 2002 [ RELATED]
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If it has been open or empty for some time, then a new receiver dryer is a good idea, since the old one is full of moisture. In any event, you will have to draw a good vacuum on the system and hold it for 45 minutes or so to remove any residual moisture. Then refill with the correct type and quantity of refrigerant.
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