[Supras] R134a pressure switch; buying refrigerant

[Bob]

Most of Interdynamics information isn't worth the paper it is written on.
They say that their retrofit kits will fit nearly every car but it doesn't
fit a GM or Toyota, I guess the two biggest vehicle manufacturers in the
world don't qualify as "nearly every car"

Anyway, the oils aren't compatible but the mineral oil seems to collect in
the compressor and the receiver dryer.  That isn't such a bad thing because
just sitting in the compressor it lubricates better than ester or pag oil
and you should change the drier anyway (not that Interdynamics suggests
that). 

Interdynamics also don't suggest vacuuming out your system before you
retrofit and that is just plain stupid for so many reasons. 

Interdynamics suggest Ester Oil and most of the A/C techs I talk to stay
away from it. It is kind of a generic one size fit all oil.  I don't have
any direct experience with ester oil failing but I also haven't heard good
things either. 

The usual rule is that you don't need to flush out the mineral oil because
it fills the pores on the old style hoses and prevents them from leaking the
smaller molecule of R134a. It just takes up space since it doesn't flow with
R134a. 

Usually a lot of the mineral oil is trapped in the receiver drier it goes
away with the old unit.

I have converted several Toyotas and I have had good luck. They even work
fine in Miami Florida. I did change the compressors on a couple of them but
that was only because they had failed clutches and it wasn't much more to
replace the unit vs. the clutch.

Bob
 
-----Original Message-----
From: Supras-bounces at supras.com [mailto:Supras-bounces at supras.com] On Behalf
Of berniek at technicaldevelop.com
Sent: Friday, May 05, 2006 10:30 PM
To: Jim Wooden
Cc: Supras at supras.com
Subject: Re: [Supras] R134a pressure switch; buying refrigerant

Jim:

    I'm surprised you made out that well without changing hoses, some of
which are permeable to R134a.  Hope you got all of the R12 mineral oil out
of the sytstem, as the oils are not compatible between refrigerants, despite
what Interdynamics claims.  I've done some electronic design work for them
on their air compressor line, and in my opinion, I've never seen such a
schlock operation (from an old building in Brooklyn).  

    Of course, you could also install a manual switch as a short term fix.  


            Bernie
  ----- Original Message ----- 
  From: Jim Wooden 
  To: berniek at technicaldevelop.com 
  Sent: Friday, May 05, 2006 9:14 PM
  Subject: Re: R134a pressure switch; buying refrigerant


  Hey Bernie!
  THANKS for the tips!

  I think the higher hi-side pressure of R134 may be what broke my HP switch
dang it! 
  It was just such a clever way to kick the fans in to boost AC performance
- I miss it.
  I like your suggestion, the R134 is not really that expensive, so I could
vent it, quickly replace the switch and then recharge.
  Even after 20 years, my system is all original (except for some o-rings
between the condenser and the HP piping that are what caused the conversion
to R134a). So I may be on borrowed compressor & dryer time here anyway
<sigh>.....................

  Thanks!
  Jim

  At 08:17 PM 5/5/2006, you wrote:

    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.  
     
        (balance snipped to save server space, already posted)
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