Yesterday, on the first really hot (90F) day of the year so far, I noticed
some interesting behaviour on the part of the AC system in our '97 Trans
Sport w/rear air. With both front and rear blowers going, the outlet temps
front and rear were cool (cool enough, but not as cool as I remember last
summer.) But, moments after shutting off the rear blower, the temperature of
the air from the front vents would rise quickly to about ambient temp. On
turning the rear blower back on, the temp from the front vents immediately
Some additional symptoms - starting a few months ago (in winter), when the
AC would be running with the defogger in coldish temps (app. 40F), I would
hear what I can best describe as a 'thrumming' sound, proportional to engine
RPMs, coming from both the rear AC unit as well as from under the front
dash. The sound would disappear with the AC compressor off. The compressor
also sounds louder than I remember it last summer.
I've done a little surfing and found some references to a TXV which operates
in conjunction with the rear blower switch. Is something going on with the
TXV in my vehicle? If not, is the system simply low on refrigerant? Oil? Or
is it something else?
Thanks for any advice anyone can provide.