Straight 134a is only a single compound.  Since it is not a mixture,
the composition will not change if some leaks out.  Of course if the
leak is serious, it should be fixed anyway.
   Some of the blends will have some molecules that penetrate thru old
hoses faster than other molecules.

Larry A.

On Thu, Jan 28, 2010 at 12:25 AM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> You need approximately 30 psi. Pushing the valve is not much of a test. If
> you can't identify the high/low pressure switches and you don't know how to
> use gauges you may want to get some training. R134-A is a refrigerant that
> does not take well to being topped off. Some of the chemical leak at faster
> rates than others and topping off gives a mix that does not work
> efficiently. In general if you need 10% or more the system needs to be
> evacuated (and the bad stuff recovered) and filled with new.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Keith Ovregaard
> Sent: Wednesday, January 27, 2010 9:59 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: AC relay question
>
> Good question, BenT
>
> There seems to be enough pressure in the system. I gave the test port
> valve on the low side a tap and it gave me a short hiss. Didn't bother
> to put a gauge on it because it didn't seem like a pressure sensor
> issue at that point. The system was topped off in Sept., I think.
> Maybe I should look into testing the pressure switches just the same.
> Anyone know how to do a bypass test?
>
> Keith O
>
> On Jan 27, 2010, at 6:45 PM, BenT Syncro wrote:
>>
>>
>> Do you have enough refrigerant in there? IIRC, compressor will not
>> engage if you are running low.
>>
>>
>> BenT
>>>
>