If your external surface temps are below 32 degrees, the likely culprit is your low side pressure switch. The Delorean cycles its compressor on and off to meter freon into the evaporator. Because R134 doesn't contain chlorine, the drier doesn't seem as critical to me. The old R12 would react with moisture to create acid that would eventually eat through the thin walled metal components. Of course the boiling point of R134 is below 32 degrees, so you do need to ensure that there's no moisture in the system (otherwise it will ice up internally). My experience has been that trying to remove components from 30 plus year old A/C systems usually causes more problems than leaving the components in place (with the notable exception of the compressor, which is designed to be removed). The metal used is *VERY* thin. You can easily kink and bend it trying to free the rusty old nuts (the way I see it, if the fittings are that rusted together, there's no need for O rings anyway!). I have systems that leak freon, and the cheapest and easiest solution is just to top them off as necessary (BTW: R134 is the exact same stuff used in those Dust-Off keyboard cleaners -- I don't see any difference in my little leaks and everyone else spraying their computers). As long as the system doesn't leak below atmospheric pressure you don't even need to pull a new vacuum. Regarding oil: The two most common R134 oils over here are PAG and Ester. Because it is mineral based, Ester oil mixes better with however much R12 oil happens to be in the system (I've converted some of my cars with the old compressor and oil in place, with identical results to a new compressor & oil). People tend to go crazy with oil anyway. Remember: oil is there for the benefit of the compressor. Because it doesn't evaporate, too much oil elsewhere will gum up the works. I've had to blow out evaporators when they were full of oil and the freon couldn't get in to evaporate. Those cans of oil designed for the low side port are particularly insideous -- a nice idea, but most of the oil ends up in the evaporator. An A/C compressor only needs a couple of ounces anyway. Because condensors work the other way around (from the top down) oil won't bother them. Oil doesn't evaporate when pulling a vacuum either -- if the system has too much you need to blow it out (the compressor itself can be removed and tipped upside down). Most flushing fluids are mineral based (I've been advised to use plain old paint thinner). Even though flushing fluid will evaporate when pulling a vacuum, I can't help but think that some of it ends up left behind in the accumulator, absorbed into the hoses, etc. Ester oil will of course react better with residual flushing fluid. "Stop up" products of any sort (radiator, transmission, etc) usually cause more problems than they cure. Because they circulate throughout the whole system, they gum up things you don't want stopped up. The only product I've ever seen suitable for such are the tubes of aluminum powder that parts houses used to sell for cooling systems, and even it would accumulate in/under the radiator cap. Bill Robertson #5939 >--- In dmcnews@xxxxxxxxxxxxxxx, "Kevin Milliken" <kevin.milliken@...> wrote: > > If you are changing from R12 to R134a > > Option 1 > > I have just been through this loop in the UK, after talking to > quite a few A/C guys and manufacturers the correct thing to do is replace > all the flexible > hoses which has now been done on one delorean. THE MOST important item to > change is the drier under > the front wheel arch, If you dont you are asking for problems, it is > "supposed" to be changed > every two years but if it is running o/k on R12 and are notchanging from R12 > to R134A.then leave it. > > The result of this is R134A A/C running at 3.8 degrees out of the vents and > the doors now freeze on the outside. > > Option 2 > > If your hoses are o/k then change the drier as above, then have your a/c man > use the new R134a oil > which is used when changing from R12 to R134A (this oil is very, very > expensive about £50.00 per half pint > about $100.00) it is not the normal R134A oil. This is used to lubricate the > pump and coat the inside of the > hoses. DO NOT under any circumstances let your a/c man use a sealer > compound. This will wreck your a/c > if you have a problem later. Sealer compound is designed to be used on old > cars which need a quick fix > and will be sent to the breakers yard after a year or so, even the > manufacturers of the sealers say dont use > it. > > I have gone through Option 1 and about to go though Option 2 on another > Delorean > > If you need any other info let me know. > > Kevin > > #5959 > #10163 To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/dmcnews/join (Yahoo! 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