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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2007R12 to R134a conversion tips?
I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. I'll be doing the repair myself. I've got a new line, dryer and O-rings. I also have an 8 ounce can of ester oil and several cans of R134a refrigerant. I know that there is no R12 left in the system (schrader valve has been loosened and there is no pressure). I also know that at least one can of stop leak and one can of Duracool (Propane) has been used in this system. At this point the system has no pressure and contains R12 oil and stop leak fluid as well as some residual propane. At this point I know that I should be doing the following: - Install the new R134a fittings to the system - Flush the current system and remove the R12 oil and other contaminants - Replace the line and dryer, using new O-rings - Evacuate the system to at lease -29lbs for 30 minutes or more - Add the can of Ester oil - Fill the system with 20 ounces of R134a (Normally 24 ounces of R12 in this system) My questions are these... - Can a shop flush and evacuate the system without recharging afterwards? Will the system hold the vacuum for an hour until I get the car home and recharge it? - If I have a shop flush and evacuate the system I will need to have the new hose and dryer already installed. Will they be "contaminated" by the flushing? - Is there a method that I can flush the system myself and be sure that I've got the oil and contaminants out of the system? Thanks! > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. > I'll be doing the repair myself. Almost forgot... Are the schrader valves used in car A/C different from tire schrader valves? They seem to be identical physically. > > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. > > I'll be doing the repair myself. > > Almost forgot... Are the schrader valves used in car A/C different from tire > schrader valves? They seem to be identical physically. Yes, different. >> > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) >> > line. [quoted text clipped - 5 lines] > > Yes, different. I'm not having any luck finding AC schrader valves on Google. > >> > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) > >> > line. [quoted text clipped - 7 lines] > > I'm not having any luck finding AC schrader valves on Google. ANY parts store should have them. Before I went through all the rigamorole you're planning and assuming you didn't have any hard parts failure (only the burst hose) I'd try pulling the system down and charge it using the ester oil. Most will cool fine and should you encounter a problem you're not out much. > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. > I'll be doing the repair myself. [quoted text clipped - 19 lines] > My questions are these... > - Can a shop flush and evacuate the system without recharging afterwards? I don't see why not. > Will the system hold the vacuum for an hour until I get the car home and > recharge it? It better. > - If I have a shop flush and evacuate the system I will need to have the > new hose and dryer already installed. Will they be "contaminated" by the > flushing? The dryer should be installed after the system is flushed. Actually, a proper flush involves disconnecting each flushable component and flushing with solvent followed by compressed air or nitrogen. If the new hose is not installed, it pretty much defeats the purpose of evacuating the system, no? Properly done, flushing will not contaminate anything. Two components that are never flushed are the receiver/dryer and the compressor. > - Is there a method that I can flush the system myself and be sure that > I've got the oil and contaminants out of the system? Given that your system already -has- sealer in it, there is no way to be even remotely certain that all contaminants are removed. Also, since you are flushing the system, why use the ester oil? ester oil is used because it is compatible with the old mineral oil already in there, Pag would be a much better choice as long as the mineral oil is being removed. You DO need to determine the exact oil capacity of each component in the AC system, (condenser, evaporator, compressor, dryer) and add that exact amount to each individual component after all oil has been removed/flushed. 8 oz of oil may be correct, it may be too much, it may be too little. If it's too much, you risk slugging the compressor with a non compressible, and cooling will be reduced. If too little, you'll burn up the compressor in short order. > Thanks! >> My questions are these... >> - Can a shop flush and evacuate the system without recharging [quoted text clipped - 6 lines] > > It better. OK... I was thinking that the AC system was meant to be pressurized and that the vacuum would "suck" the shrader valve open. >> - If I have a shop flush and evacuate the system I will need to have the >> new hose and dryer already installed. Will they be "contaminated" by the [quoted text clipped - 4 lines] > component and flushing with solvent followed by compressed air or > nitrogen. So I will install the new line and the dryer and have the system flushed and evacuated by a shop. I assume that the shop is smart enough to disconnect the dryer before they start flushing the system. > If the new hose is not installed, it pretty much defeats the > purpose of evacuating the system, no? > Properly done, flushing will not contaminate anything. > Two components that are never flushed are the receiver/dryer and > the compressor. If the compressor isn't flushed, how do I get the old oil of of it? >> - Is there a method that I can flush the system myself and be sure that >> I've got the oil and contaminants out of the system? [quoted text clipped - 6 lines] > oil already in there, Pag would be a much better choice as long > as the mineral oil is being removed. Playing it safe... If all the mineral oil isn't removed the ester oil won't cause me grief. > >> My questions are these... > >> - Can a shop flush and evacuate the system without recharging [quoted text clipped - 9 lines] > OK... I was thinking that the AC system was meant to be pressurized and that > the vacuum would "suck" the shrader valve open. That would indicate a defective shrader valve. > >> - If I have a shop flush and evacuate the system I will need to have the > >> new hose and dryer already installed. Will they be "contaminated" by the [quoted text clipped - 6 lines] > > So I will install the new line and the dryer and have the system flushed and "The dryer should be installed after the system is flushed." > evacuated by a shop. I assume that the shop is smart enough to disconnect > the dryer before they start flushing the system. I wouldn't assume that. I also wouldn't recommend wasting a dryer on an un-evacuated system, once you install it, it will start to absorb moisture. Leave the dryer on the front seat unopened, explicitly explain to them that it is there and to be installed once the flush is completed. They have to take it all apart anyway to do the flush correctly. > > If the new hose is not installed, it pretty much defeats the > > purpose of evacuating the system, no? [quoted text clipped - 3 lines] > > If the compressor isn't flushed, how do I get the old oil of of it? Disconnect the fittings, un-bolt it and tip it so it drains. Rotate the crankshaft forwards and backwards to assist oil removal. > >> - Is there a method that I can flush the system myself and be sure that > >> I've got the oil and contaminants out of the system? [quoted text clipped - 9 lines] > Playing it safe... If all the mineral oil isn't removed the ester oil won't > cause me grief. Ester oil is an inferior lubricant, using it is NOT "playing it safe." A little mineral oil will not cause a problem, i.e., that which is stuck to the compressor internals, all other mineral oil will be gone when the system is flushed. > My questions are these... > - Can a shop flush and evacuate the system without recharging afterwards? > Will the system hold the vacuum for an hour until I get the car home and > recharge it/ Yes, a shop can flush and evacuate the system. It had better hold the vacuum. If it doesnt, you still have a leak. > - If I have a shop flush and evacuate the system I will need to have the > new hose and dryer already installed. Will they be "contaminated" by the > flushing? The new filter dryer should be installed after the flush. The hoses and other parts will be clean and dry, due to the evacuation. > - Is there a method that I can flush the system myself and be sure that > I've got the oil and contaminants out of the system? Not really. You could probably flush it, but if you dont have the ability to pull a vacuum, you are still not where you should be. They will flush out the contamination and lubricants, evacuate to "dry" the system, and replace it with lubricant that is compatible with your refrigerant. Why dont you just do the replacement of the hose, and take it to a shop for flushing, evacuation, and charge? You can get good info on changeover at www.ackits.com I have nothing to do with them, except that I use their parts and advice.. Good people to know about. >> My questions are these... >> - Can a shop flush and evacuate the system without recharging afterwards? [quoted text clipped - 4 lines] > vacuum. > If it doesnt, you still have a leak. So they pull the vacuum for 30+ minutes & disconnect the equipment. Then I drive the car home. Once in my garage the system will still be at 29in hg? I then add my oil and R134a. >> - If I have a shop flush and evacuate the system I will need to have the >> new hose and dryer already installed. Will they be "contaminated" by the [quoted text clipped - 3 lines] > other parts > will be clean and dry, due to the evacuation. > Why dont you just do the replacement of the hose, and take it to a shop > for > flushing, evacuation, and charge? Cost is the big thing. I also prefer to do things myself when possible. Thanks! "Noozer" <dont.spam@me.here> wrote in message news:Dk1ki.96052 > So they pull the vacuum for 30+ minutes & disconnect the equipment. Then I > drive the car home. Once in my garage the system will still be at 29in hg? > I then add my oil and R134a. Yes. Remember they the system will have none of the old lubricant after the shop properly drains and flushes the system. You can have them add the concentrated lubricant at the shop, after they finish cleaning the system, or you can add it yourself using the 134a charge cans with lubricant. Be sure what the shop is giving you, because you dont want to do both. The last time I charged my (leaking) van, I used both the pressure readings, as you plan to do, and I also weighed each can before and after additions of refrigerant. The pressure was exactly what it was supposed to be when the weight of refrigerant was correct. I have now pulled mine down to replace the leaking evaporator core, which was the cause of the problem in the first place. It was more of a job than I had figured, mainly because I had never done this on a van before. "The book" would lead one to believe that the core case comes out a bit easier than it actually does. With atmospheric pressure at just under 15 PSI, how do you plan to "Evacuate the system to at lease -29lbs"??? > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. > I'll be doing the repair myself. [quoted text clipped - 16 lines] > - Fill the system with 20 ounces of R134a (Normally 24 ounces of R12 in > this system) > With atmospheric pressure at just under 15 PSI, how do you plan to > "Evacuate the system to at lease -29lbs"??? Doh! OK... 29 inches of Hg then. > > With atmospheric pressure at just under 15 PSI, how do you plan to > > "Evacuate the system to at lease -29lbs"??? > > Doh! > > OK... 29 inches of Hg then. A proper evacuation would be; to 500 microns, isolate vacuum pump, vacuum not to rise above 750 microns. I fail to see the savings of having the shop do all the work except adding the r134 and doing that yourself. It seems to me you need to talk to the shop you plan on having do this and discuss the prices they will charge for the whole thing. After all the other work recharging is nothing since it is already hooked up to the machine. >> With atmospheric pressure at just under 15 PSI, how do you plan to >> "Evacuate the system to at lease -29lbs"??? > > Doh! > > OK... 29 inches of Hg then. >With atmospheric pressure at just under 15 PSI, how do you plan to >"Evacuate the system to at lease -29lbs"??? The same way my congressman manages to spend Federal money that doesn't exist. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >>With atmospheric pressure at just under 15 PSI, how do you plan to >>"Evacuate the system to at lease -29lbs"??? > > The same way my congressman manages to spend Federal money that doesn't > exist. Yeah, but he has a powerful machine in place to suck it out of us all. SignaturePostulate a group whose intent is to destroy the United States from within via anarchy and bankruptcy. The actions of the United States Congress are completely consistent with the actions one would predict from such a group. > I've got a 1993 Mazda 626 with a ruptured discharge (high pressure) line. > I'll be doing the repair myself. > > I've got a new line, dryer and O-rings. I also have an 8 ounce can of > ester oil and several cans of R134a refrigerant. <snip> For those who were wondering... THIS is why I want to do this work myself: F/S - Flushing Solvent 1.00 Litres $30.45 / Litre $30.45 G R134A - Refrigerant 48.00 Units $1.54 / Unit $73.92 G 59099 - Ester Oil 5.00 Units $5.16 / Unit $25.80 G Labor $294.00 Subtotal $424.17 Shop Supplies $23.52 (GST) 6% $26.86 Totals $474.55 For that money I could drive 6 hours across the border, get a hotel room for the night, buy a set of gauges and a decent vacuum pump and drive home and still have money left over for a steak and seafood dinner. Don't why I'd cross the border... I saved about $400 by purchasing my motor mounts in the US instead of Canada. |
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