On Fri, 16 Oct 2015 08:51:21 -0400, "David L. Martel"
wrote:

Ashton,

. Why would it do so immediately
after starting and while idling yet never do so while running down the
highway for hours on end?

You have very little data so concluding that it's a "starting" phenomenon
may not be correct. You may be jumping to a conclusion.

Dave M.

There is little data but all three times it was immediately after
starting while idling. To me that would seem like the easiest part of
the work day for the AC yet it overpressureized and "blew". I keep
trying to figure out what there would be about the "refrigeration
cycle" that would somehow create such a high pressure within a couple
minutes of system startup. To blow off the high pressure valve it has
to get to something like 400+ psi. Even with it sitting in the
driveway as I finish putting 134a in it in 95 degree temps it only got
to around 325 psi at 2500 rpm. At idle it's in the 200's. The only
things I can see that would make it blow are a blockage or oil or
freon slugging. I can see how a blockage could happen but if there is
stuff in there that's going to block something it seems like it would
have happened at high speed "the day before", not "today" when the
system is just loafing along at low rpm's. Is there something about
startup that would create an oil or refrigerant slug in the
compressor?