Have a 2001 Sentra GXE and noticed something for the first time that is quite unusual. With the mode function knob in the Vent position (full CCW) the air flow out of the left hand (center) register varies as a function of the temperature knob setting. No kidding!!! Fan on high
Temperature Setting on Hot=== Almost No air out of LH Center Register, Lots of air out of RH Center Register.

Temperature Setting on Cold=== Both Center registers have a full air flow out of them.
Obviouly, what this says is that the air flow out of the center register(s) is a function of the temp knob setting when the system is in the Vent only mode. Anyone else??

I have heard a few people talking in the past about a sew of them having the problem of the air blowing out stronger on some of the vents harder than the others.But I myself don't experience this....