Re: how do you make the a/c colder?

["Fred Munro" <munrof@isys.ca>]

-----Original Message-----
From: R. Cummings <cumm@flash.net>
To: FRED MUNRO <munrof@isys.ca>
Cc: quattro@coimbra.ans.net <quattro@coimbra.ans.net>
Date: Thursday, June 04, 1998 9:34 AM
Subject: how do you make the a/c colder?


>Original Message
>>Hi Adam;
>>
>>    You lose 20% of the cooling capacity when you change from R-12 to
>>R-134a. In addition, the pressure generated by the R-12 compressor is not
>>high enough to take full advantage of the R-134a characteristics.
>>    BTW, R-134a is a mixture of propane and isobutane. Something to keep
in
>>mind in a front end collision with that condensor hanging out in front.
The
>>automotive engineers apparently believe the risk is acceptable, but I
would
>>think there is a good chance of a fireball with a couple of pounds of
>>barbecue fuel spewing out of a ruptured condensor.
>>    I don't know of a way to make the system run colder if it is properly
>>charged and the propane/isobutane mixture is right. One of the problems
with
>>R-134a is that the isobutane is lost preferentially and the mixture gets
out
>>of proportion, resulting in loss of cooling capacity. This apparently
takes
>>3-4 years and the system has to be drained and re-charged. Fortunately,
>>R-134a is cheap.
>>
>>HTH
>>
>>Fred Munro
>>
>Wow!! How do these rumors get started. R134a is NOT a mixture and it is not
>flamable. Many states have laws that flamable refrigerants may not be used
>in mobile A/C applications. R134a is the ONLY replacement refrigerant
>recommended by the vehicle manufacturers.
>
>There are some SNAP approved replacements that have 4 or 5% butane to carry
>the oil but in that quantity is not considered dangerous.
>
>R134a runs about 20 psig higher than R12 on the high pressure side for the
>same refrigerant temperature but hose life and compressor life are as much
a
>function of temperature as pressure.
>
>We have not found a 20% cooling capacity loss with R134a unless the
original
>condenser is extremely marginal. If that is the case an additional
condenser
>fan usually cures the problem.
>
>It requires about 15% less R134a to charge a system than R12 so it is easy
>to overcharge if not paying attention.
>
>Bob Cummings   87 Coupe GT
>

    Hi Bob;

    You are correct. The error was mine. My most sincere apologies to the
list for this erroneous
info . I misread an extensive posting on replacement A/C
refrigerants at www.dcc.edu/vettenet/acfaq.txt which describes how to make
your own R-12 replacement from isobutane and propane and somehow inferred
that this was the composition of R-134a.
    I guess this is one way these rumors get started! Thanks for the
correction, Bob! I feel more comfortable about R-134a now.

    Sorry!

    Fred Munro
'91 200q  253k km