[Supras] R134a pressure switch; buying refrigerant

[berniek@technicaldevelop.com]

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)