R134a retrofit questions?

[Kunz, Bob]

You know after 20+ years for the first recharge that's pretty good. My '86 5k lost a little refrigerant over the years and I've just had to top it up once so far.

There's more to 134a conversion that what you describe on these vintage cars. If you actually have a leak, it will get worse since R134a is less dense than R12. This could also cause slow leaking through the actual hoses. But R134a is a lot cheaper than R12 but IS still available with prices coming down. You should replace all seals with new ones.

Failures (i.e. not as cool) on the conversion are almost always due to mineral oil not being completely evacuated. Some system configurations will be OK, others not. If oil pools in components it will restrict flow and cause inefficiencies. Usually the conversion involves flushing the system to remove all mineral oil.

Then you should really take the compressor off and drain the remaining oil in there. You don't flush the compressor.

Having done that you can use PAG oil as opposed to ester which is a compromise to let you keep some mineral in there. The correct amount of oil in this GM based system is 10.5 oz. You need to distribute it some as you close up the system. It won't all fit in the compressor anyway, only about 2 oz goes in there.

Then of course you need to use a real vacuum pump and get the system down below 100 microns, find your assembly leaks. Hold 220 microns for an hour to boil off all the water (this would be why you do this in the summer as opposed to now - it's easier to get the water out when the ambient is hot), then add your refrigerant.

Lots of folks have adjusted the evaporator sensor down to just above freezing. In high humidity areas this is risky since its purpose is to keep the evaporator from freezing. This system is a chill/re-heat type so the refrigeration runs to the set temp of the evaporator. If you set it low, the compressor will run more. Your choice.

Back to your original question... at this point I'd go source some R12 and charge it up. You might find that's all you need for the next 10 years.

--bob
'86 5Ks Avant
'02 TTQR
'06 GTI
'07 Q7 4.2

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On Behalf Of Dave Yentema
Sent: Wednesday, October 22, 2008 11:03 PM
To: quattro at audifans.com
Subject: R134a retrofit questions?

hey guys, got a couple of questions about converting the ac in my car
(875kt)

she has never been retrofitted to 134, and from lack of use 90% of the r12
is gone, its low to the point that the comp won't even run(I tested this by
jumping the connectors on the low pressure switch) So after weighing out all
the options, i've decided that the conversion is my best bet right now.

I've seen my dad do the conversions before, and whenever he did it
professionally he would just evacuate the r12, change the fittings, drop
some ester oil in and charge it up with 134 (Even though this isn't the
recommended procedure, it always worked) . He knows his stuff with AC, does
everything the old fashioned way with just the manifold gauges and knows
exactly what lines to touch, etc. Having him help me on this isn't really an
option for this.

This is what I'm picking up:

-New receiver/drier (from AutohausAZ)
-134a retrofit kit, not the one with the oil, but its got all the fittings
and o-rings I'd need (also from autohaus)
-Polymax2 oil http://www.autoacsource.com/store/coolzone_oil.html
-Variable orifice
tubehttp://www.acsource.com/index.asp?PageAction=VIEWCATS&Category=273




I know that the system holds about 39oz of R12, and it'll take about 85% of
that with 134, so about 33oz?

and how much oil does it take? I read somewhere it takes 8oz but i'm not
sure.

also, any reason  why I can't do all of this while its getting colder
outside? or should I wait till springtime to try and fill er up so to speak

any suggestions would be awesome

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