Daniel!

You might be right about a slow leak,
do this, turn your system of turn key to second
position and see if pump stops and stays off,
do this test at every mode heat and cool and defrost, if any keeps running or comes right
back on then there is a leak,
and if you wish I can e-mail you a nice clear
diagram,
also rear vents I say your rear vacuum converter is shot and or leaking, I can show you on the
diagram waht this looks like.

Sincerely Jens