Tom,
Would suggest that 'blowing a hose after a while' had nothing to due with
the R134a gas. At 60oC [140oF], R134a is ~230 Psi, R12 is ~210 Psi. If
she's gonna blow at 230 Psi, she'll also blow sooner or later at 210 psi.
Hose blowout would more likely be caused by poor qulaity hoses, poor
workmanship, incorrect crimping of hose, etc - any number of factors.
What is 80% charge? Don't even have a clue what that refers to so you're
going to have to fill me in on that one.
Fan will normally run on high. Your getting rid of all that heat in your
cabin through the condenser - gotta have air to take it away. Also depends
on what the ambient temps are -you didn't mention this?
All A/C systems will/should have a High Pressure Cut-out switch to protect
against excessivly high pressures. 'Don't leave home without one'
Why:
1. You might be running in the Sahara desert and its 60oC (140oF) outside.
Your A/C isn't designed to run to those high temps. You'll damage your
compressor, blow a hose, develop leaks, take your pick.
2. You might get a newspaper blown in front of your condenser which stops
the airflow through it - refer to item 1 for consequences.
3. You might get a blockage in your piping somehow - say goodbye to your
very expensive compressor

Need I go on - get a High Pressure Switch. Anymore questions - just email
me.
I design Bus Air Conditioners for a living.

David Del Ben
85 Vanagon

-----Original Message-----
From:   TSmith5041@aol.com [SMTP:TSmith5041@aol.com]
Sent:   Friday, September 01, 2000 1:10 PM
To:     ddelben@airinter.com.au; vanagon@gerry.vanagon.com
Subject:        Re: D.I.Y. R-134 Kit AC Recharge advice

Have successfully converted my van's a/c system to R-134A. 1st attempt blew
a
hose after a while. Had them rebuilt with modern barrier hose. I went with
an
80% charge but the hi-pressure switch runs the fan on high a lot. The EPA
web
site on conversion mentions using a cutoff switch on the compressor to
control excessively high pressures. Anyone have any thoughts on or
experience
with this?

Tom Smith
83.5 Westie