When you hit the little green lighted A/C button, nothing happens, no usual change in engine sound etc. Checked it out, clutch does not engage. Have power at relay, fuses are good, narrowed it to the little green lighted A/C button. Does anyone know how to access it, can't get the dash apart around switch, radio, etc. area.

Isn't the A/C button blue? The green is for recuirculating of inside vs. outside air.

In the later models, the A/C and circulating air button are both green.
I'm not sure what the problem is, but if you need to get your dash apart, I have a link that should help you. Note, this is for a 2004.
http://www.diycarstereo.com/xterra.html