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Old 05-27-2008, 10:01 AM
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AC Retrofit questions

With the price of gas, Iíve been driving my 1988 Ĺ Escort back and forth to work a lot more often lately. Since the weather is warming up, I was thinking that I should get the AC working on it again (it was my motherís car, itís got 35,000 miles on it and the AC has never been serviced). Itís really low on R-12, so Iím planning on flushing the system, replacing the accumulator (which gets me a new hose too) and retrofitting with R-134a. Does anyone have any recommendations on the oil to use? Iíve heard that Ester is better for a R-12 retrofit than the PAG oil used in a R134a system, being nore compatible with any residual mineral oil. Does it matter if Iím going to flush it anyway? If PAG, what viscosity (46, 100, 150)? Also, it doesnít look like the orifice tube is replaceable without cutting it out and using a repair kit. Any thoughts on this? Thanks.

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Old 05-27-2008, 10:29 AM
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Hi: I'm going to move this to General Rodding Tech.

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Old 05-27-2008, 03:50 PM
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IMO don't do it! Every system I have seen converted died soon after, including two of mine. R12 can still be found and if the system is still good it will not cost much more to have it topped off with the right gas than to go to the expense of conversion. Not only will it last a heck of a lot longer but it will cool a lot better also. A buddy of mine that does auto AC told me they refer to those conversion kits sold at Wal-Mart, etc, as "Killer Kits" and that the drop-in replacement coolants such as "Freeze 12" are even worse and they will destroy your system in short order. According to him most of the replacement blends will not carry lubricating oil through the system properly leading to compressor failure.
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Old 05-28-2008, 04:28 PM
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R-12 might still be available, but not without a license to someone that wants to service their AC system themselves. I've done some more research and it looks like Ester is the oil of choice on retrofits, since it can tolerate any traces of the original oil left in the system. I'm planning on flushing the system and replacing the accumulator before I vacuum it down anyway. As far as cost goes, the R-134a is cheap and I have all the tools.

Last edited by MAUSS; 05-28-2008 at 04:33 PM.
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Old 05-29-2008, 07:20 AM
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I thought some of the AC guys might chime in but apparently not. As I said I killed two of my systems before I learned better and I have seen several others go the same way. The ester oil is used with those conversions to eliminate compatibility issues but it does not work well with R134a that's the reason 134 systems use PAG. While the ester will be compatible with any remaining factory oil it is not as compatible with the R134a and will not mix properly to be carried through the system. Using PAG in a system that already has R12 is not a good option either because there is no practical way to remove all the remaining mineral oil and mixing PAG with that residue is not good either, ester is used because it is the lesser of the two evils. This was the way it was explained to me and it appears to be the case. If your system is sound you would be far better off to just change that accumulator, the orifice tube (there is a simple tool available to do this) and the line fitting seals (O-rings) then take it to a shop and have the system evacuated and recharged with the proper gas. It will last for years if you do this and will cool much better than the 134 used in a system designed for R12. I thought I would take the cheap and easy way but as usual the cheap way out leads right back in!
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Old 05-29-2008, 09:48 AM
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Let me chime in with my 2 cents worth. When retro fitting to R134a you need get a compressor kit designed for use in a R134a system. These kits come with a new compressor, reciever drier/accumulater, the correct fixed orifice, an o'ring kit, flush, and the correct grade of pag oil for your system. If you have to, get more flush and keep flushing the condenser and evaporater untill you get clean flush coming out. Do not use an oil based flush, as it leaves a film and does not dry completely out. After you have the system back together evacuate for ten minutes, turn off your pump and gauges and watch your gauges for 10 minutes for any vacuum loss. If there are no leaks start your vacuum pump and find something else to do to occupy your time for the next hour and a half to two hours. This will ensure that all of the moisture is out of the system. Add just enough R134a to get the compressor to just stop cycling the raise your idle to between 1800-2000 rpm. At this point if it starts cycling quickly add an ounce or 2 at a time, watching your gauges. You will want your high side pressure right at 225 psi and your low side as close to it's cut off pressure as you can get it. If done right it will be in the low to mid 30's coming out of your vents. Down right cold!
As for a retro fit system not lasting and failing, this is a misnomer, as I have not had a single system failure yet, and I do 6-10 retro fits a year. I do not advertise and I get all of my new customers from referals.
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Old 05-29-2008, 10:44 AM
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Doing it that way will work because you have all the right parts and will have pretty much eliminated the contamination problem. The problems I had and the others I am aware of were all done the way Mauss has suggested he wanted to do, just replace the accumulator/dryer, vacuum the system then add The 134 and oil. The shop that replaced both of my systems did just as you suggested and I have had no more problems but when I wanted to just flush out the system I was told that usually does not work very well because of oil that will be left in the compressor, etc.
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Old 05-29-2008, 10:59 AM
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I believe in doing it right the first time, or don't do it at all.
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Old 05-29-2008, 04:30 PM
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Actually, I plan on removing the compressor and draining whatever oil is in there, then flushing everything (except the accumulator, which will be replaced of course) before evacuating the system and recharging. There will be very little of the original mineral oil left in there, which should be tolerated by the new Ester oil. From everything I've read, Ester is compatible with the R134a and is prefered over PAG for retrofits (unless you're replacing everything anyway). Basically I have nothing to lose, since the AC in the car hasn't been functional for years anyway.
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Old 05-29-2008, 07:48 PM
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A/C work is one of the main reasons I am self employed. I had previous employers and service writers force me to do A/C retro fits the way you are planing to do it. I was not pleased with the system performance and rarely saw the customer back again for any other type of work. Having worked in this area for so many years I am well known for A/C performance and get new customers from referrals yearly. I've had 2 this spring already. I know what it takes to prevent comebacks and return customers, and if you can afford to get a new compressor designed to be used with R134a freon, and follow my directions you will be money ahead in the future, by not having to tear it down to replace your junk compressor.
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Old 05-30-2008, 10:44 AM
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No need to get too excited about this... I'm the "customer" and the AC on that car hasn't worked in years anyway... I have all the equipment (vacuum pump, manifold gauge set, etc) from working on my other vehicles that are already R134a equipped. If it doesn't work out, all I'm out is the price of the accumulator ($48), a bottle of oil and a couple of cans of R134a ($3 a can, bought by the case at Sam's Club). Like I said, I'm flushing everything anyway. I just don't want to pay someone a lot of money to do the work on a 20 year old car if I can do it myself.
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