Pretty much every good A/C system I've seen can blow 38-40 degree air. I don't usually see freeze-up until the air temps are about 35 degrees F. I think you're really over-estimating a 10-15 degree difference between coil temp and air temp- its more like 3-5 degrees tops. Unless all the fine finning is corroded away on the coil.
Air has needs, too.
Paul ( pjm @ pobox . com ) - remove spaces to email me 'Some days, it's just not worth chewing through the restraints.'
HVAC/R program for Palm PDA's Free demo now available online
About 45 to 50 degrees on Max. I could probably bring that down a lot by installing a pusher fan.
Dan already knows this, but I'm actually a big fan of STICKING WITH R-12 almost all the time. But this particular car had an A/C system that had been hanging open for 10 years, and needed serious flushing and refurbishment anyway, as well as a replacement condensor (stock unit from a junkyard). I did the conversion just to see how "bad" things might be for my other cars in the future, and was pleasantly surprised. The one redeeming thing about an R-134a conversion is universality. If I'm driving from home to Podunk Montana in July, I can always find a shop that will service an R-134a system. Not so R-406a, Freeze-12, etc. etc. etc.
I'm now into my second Texas summer on this sytem, and knocking wood... I realize that compressor lubrication issues could crop up unexpectedly at any time, but so far so good.
Bzzt. Wrong.
Paul ( pjm @ pobox . com ) - remove spaces to email me 'Some days, it's just not worth chewing through the restraints.'
HVAC/R program for Palm PDA's Free demo now available online
I see your "Bzzt" and fart in the general direction of your "wrong."
The shortcoming at idle is related both to compressor capacity and to condensor air-flow, but in the case of this car its the condensor airflow that dominates the problem. Sitting my Patton shop fan in front of the condensor with the car idling drops the temps down nicely, but since I do take the '69 to car shows I really don't want a Hayden pusher fan and a bunch of extra wiring cluttering up the engine bay. And the car's a CONVERTIBLE for cripes sake, the A/C isn't my top priority with it.
Try R416A. "SNAP"? Yes, Glide? Minimal. Fractionization? Very Low. ODP? Minimal to None. AKA FR12 Much better performance than R-134A(ss)
ReRe
*CBHVAC* wrote:
why...therefore,
I believed that line for YEARS. And I also believed that my old Chrysler systems with RV-2 compressors and EPR valves would be among the worst conversions imaginable.
But it turns out that if you do it right and remove the EPR valve (and install an evaporator temperature controlled clutch cycling switch instead) it works pretty well in those old systems. The main requirement is a large condensor area compared to the evaporator. Minivans and SUVs make terrible conversion cnadidates, most cars do OK if done correctly. My '69 Dodge, converted to R-134a, blows 38-degree air in 98 ambient with 50% humidity when cruising down the highway. All stock A/C components except seals and the refrigerant. Stop-and-go requires using MAX (recirculated air) to keep the temps down below 40, but they do stay below 40..
Same story with GM and other brands- doing it RIGHT involves more than just flushing and changing refrigerants and oils. With orifice tube systems, you need to switch to a Smart-VOV instead of a fixed orifice tube, just like you need to get rid of the EPR valve in EPR-valve systems.
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