Date: Wed, 18 Jul 2012 21:28:30 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: AC Question-reponse error
Content-Type: text/plain; charset="us-ascii"
Yes I made an error. R134a is an azoetrope. NOT a zoetrope. Mixtures using
it are zeotropes.
I was not fully awake during my response.
The topping off of leaking systems and improper repairs in general justify
the continuing laws, taxes, and other restrictions on the use of
refrigerants. R134a is considered as contributing to greenhouse gasses and
it is now also at risk for being phased out.
Thank you for the feedback and kind words.
Dennis
-----Original Message-----
From: Ed McLean [mailto:email99@BELLSOUTH.NET]
Sent: Wednesday, July 18, 2012 10:36 AM
To: Dennis Haynes
Subject: Re: AC Question
Hi Dennis,
A couple of details that I believe are incorrect in your recent post to the
Vanagon list. This is a personal email that is not posted to the list.
R-134a is not a mixture but a single chemical (1,1,1,2-tetrafluoro ethane)
and being a single component and not a mixture, its composition does not
change on partial evaporation and therefore cannot be an azeotrope. I
believe there was a typo in the spelling of this word.
Of course, with the R-12 substitute refrigerants that are mixtures it is
unwise to top the up for the exact reason you mentioned.
I do agree that it is bad practice to top up a R-134a system but the reason,
as you indicated, is that it is difficult to determine the proper state of
charge from pressure gauge readings. I have recently been made aware of
this difficulty by breaking several AC belts on my SubaruVanagon with a
highly modified air conditioning system (2 evaporators and 2 condensers) as
a result of topping up and over charging.
As a long time member of the Vanagon list, I have really appreciated the
valuable insight and wisdom in your many letters. Many times when searching
the archives to find an answer to a problem I find a concise explanation of
my problem and the proper method of correcting it. Thanks.
I am writing this letter as a friend and I hope that if I ever get to Long
Island I can stop by to say "Thanks" in person.
Regards,
Ed McLean
On Wed, 18 Jul 2012 00:30:18 -0400, Dennis Haynes <d23haynes57@HOTMAIL.COM>
wrote:
>Didn't you just recently add refrigerant? Not a good idea to just keep
>topping off a system.
>
>The radiator fan should be running in a low speed whenever the AC
>clutch is engaged. Either excessive head pressure or the radiator fan
>switch high speed will put the fan into high speed. If the radiator
>switch puts the fan into high speed the AC should disengage until the
>rad temp goes down. It should be a rare occaision for the fan to run in
the high speed mode.
>Usually this is a sign of an over charged system.
>
>R134a is a zoetrope. When it leaks out not all of the compounds leak
>out at the same rate. So when you just add you lose a lot of the
>efficiency and things go wrong, you can't rely on pressure readings to
>determine a proper charge. Charging should always be done be recovering
>what is left, evacuating the system, and then charging the system by
>weight. The proper fill is 80 to 85% of what the system called for in R12.
>
>Dennis
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
>Of JRodgers
>Sent: Tuesday, July 17, 2012 11:18 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: AC Question
>
>AC was putting out the barest of cool air on full at night - could not
>feel but hot air during the heat of the day. Added R134a and now it works
great.
>BUT - it seems the radiator/condenser fan up front runs as long as the
>AC is turned on - and I think that is as it should be -or is it? But
>this evening
>- while ambient temp was still quite warm, not far from home I turned
>the AC off when stopping for a light (idle stabilizer doesn't work so
>engine would stall otherwise) and when I turned it back on - I noted
>that radiator/condensor fan didn't work - didn't turn on.
>The AC continued to put out cold air - but now fan doesn't run - which
>incidentally up to now sounds like a jet engine running.
>
>Can anyone tell me about how this is supposed to work - and do I have
>something wrong? Or am I fretting over nothing?
>
>Thanks,
>
>John
