<VV> Charging AC

[Frank DuVal]

You are installing a 34 volt electrical system? Gee, the auto makers are 
talking going to 42 volt systems here shortly. You could wait until the 
parts are cheaper. Got a good deal on military radio equipment and want 
a little more power than the 28 volt system gives?

Oh, R 134a refrigerant!

Rule 1:  the charge with R 134a will be less weight than the R12 system. 
80% is a good starting point, but some systems like much less R 134a.

Rule 2:  only a half hour at vacuum after an air purge is way low. I 
like to vacuum them for several hours to make sure all the moisture is 
gone. But, this shouldn't cause your problems. Typically I leave the 
system under vacuum overnight without the vacuum pump on to really check 
for leaks. If it can hold 28 in hg for 12 hours then I will risk 
reinstalling R12.

You say the compressor locks up, but you do not list the high side pressure.

Rule3:  Do not charge R 134a without reading the high side pressure. It 
is very easy to overcharge R134a and blow the pressure releif vale open. 
VERY quickly climbs over 450 psi. And this is on R134a systems, not 
conversions. Just ask how I know!

You aren't charging with liquid so much you are hydro locking the 
compressor?

Rule 4: Ignore looking at the sight glass. That was for R12 and the 
converted system just isn't going to work the same way. Put tape over it 
and use gages. You did change the shrader valves with converters to the 
R143a style so no one gets confused?

Reply with pressure readings.

Frank DuVal



Smitty Smith wrote:

>Smitty says:  I am changing my wagon system over from 12 to 34.  I have a new comperssor and dryer.  System has been flushed and air dried.  Expansion valve has been removed and cleaned.  System was made up of junkyard parts except for the evap which is Early Corvair.  It worked fine on 12 till last summer.
>  Upon charging systen it was drawn down to 28-29" which it held without loss for a half hour.  Charging it, I can only get about a can and a half of 34 in it and the compressor locks up.  Belt is a little too tight if anything.  IDEAS ???
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