I wouldn't worry about it until something blows (usually a high pressure hose
which is actually routed under the van so not a danger to anyone inside).  I
mean there are lots of vehicles out there with R-134a in their system that
never have any problems.  If your system was marginal before you put R-134a
in it then it defineatly won't last long after the retrofit (the pressures go
up and it puts more stress on everything).
Hope you have many cool summer trips with no problems.

Ken Wilford
http://www.vanagain.com
John 3:16
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