[Supras] R134a pressure switch; buying refrigerant

[Gregg Bradstock]

BernieK

Its always a pleasure reading your posts, you have a lot of knowledge and 
give it freely.   I had my conversion done a few years ago.  The mechanic 
said it might not cool as well, but I culdn't tell the difference.  Other 
than a connector change and purge, I'm not sure what he did.

Gregg
87NA


>From: berniek at technicaldevelop.com
>Reply-To: berniek at technicaldevelop.com
>To: Jim at WoodenU.com
>CC: Supras at supras.com
>Subject: [Supras] R134a pressure switch; buying refrigerant
>Date: Fri, 05 May 2006 20:17:22 -0400
>
>Jim:
>
>     At least as of last year it was not illegal to vent R134a to the 
>atmosphere, as it is not a clorofluorocarbon as R12 is.  Beyond that, the 
>temperatures and pressures are different for R134a than for R12.  It may be 
>that your pressure switch is OK, but you may really need one for R134a.  
>Its been a long time since I looked at this, and stocked up on LOTS of R12 
>instead of pursuing R134a, having a few old cars.  But you can find the 
>information at a refrigerant manufacturer's website, like Forane.  You want 
>the pressure-temperature charts for both.
>
>     A quick check of ebay shows that R134a is sold without need of an EPA 
>license, not true of R12.  The commercial establishments like Grainger do 
>sell only to "licensed commercial establishments".
>
>     If you ever need to get a license to buy refrigerant, you can buy any 
>one (including R-22 for home use) with just the lowest level license, 
>available by correspondence test over the internet from epatest.com.  You 
>can download a study guide first, free.  This license will entitle you to 
>work commercially on car systems, but not fixed systems, for which a 
>proctored test is required.
>
>     In the short term, you could also get an O-ring sealed tubing piercing 
>valve, and plumb it to a new pressure switch before installing it.  A 
>potential problem is that they may not be made in metric sizes.  A quick 
>check on the internet will tell you this.  There are one or two very big 
>refrigeration supply houses on the first page or two, if I recall 
>correctly.  One other problem with piercing valves is that the leak over 
>the long term.
>
>     If you vent the system slowly so as not to lose oil, you can change 
>the pressure switch quickly  so as not to get air into the system.  Just be 
>all ready to do so first.  Doing this will avoid the need of pulling the 
>system down with a vacuum pump.  When refilling it, you can get by with 
>just a low side gauge, or a "recharge" kit although a complete high and low 
>side gauge kit is best (again check ebay).  I'm sure you are aware of this, 
>but gauge port fittings for R12 and R134a are different.  Set the system to 
>maximum cool, and add R134a into the suction port just to the point where 
>bubbles in the dryer sight glass disappear, then add maybe 2-3 ounces more. 
>  You can turn the container upside down to liquid charge, but be VERY 
>careful with charging rate to avoid sucking liquid refrigerant into the 
>compressor.
>
>
>     Hope this helps.
>
>
>                 BernieK
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