We love our Tracker It goes up hills that terrify my wife.....   This month we are in Pahrump Nevada where it goes over 100f a lot.  The AC  is weak enough it hardly does anything.  We have a black Tracker with a Black convertible top so that is not so good.  The coolant pressures are correct on the high and low. The compressor clutch engages correctly.  The fan works.  When we got it it had a leaky o-ring that I replaced and also replaced the dryer, then recharged. 
  I notice that the local Trackers and Sidekicks all have the windows open.  The questions are  - Is this just a weak AC from an age when that was normal?  Can the system be improved?

Trackick's ACs don't help when it gets hotter and hotter. One way to make sure for the condenser fan working is to remove it out of the car and test it!! Look at the condenser itself if it is clean or replace it.

The fan spins. I can see it from the grille.   I also realized something else. The system is designed to cut out the AC when climbing a steep hill or accelerating. I suspect that  grinding up curvy gravel and sand foothills causes the automatic cut out to engage for more power. We noticed that going up the AC was blowing hot but on the way down it worked fine.  I wouldn't mind if I could defeat that with a switch when off road and just gear down to help power up. No idea how though.  I don't know how the system  decides to do that.
 I have now made a headliner of 2 layers of silvered reflective  roll insulation.  I will make a post with pics. It helps.

The system is designed to cut out the AC when climbing a steep hill or accelerating.

As far as I know the only thing that cuts the a/c out is an engine "over temp" condition, as the coolant temperature rises it trips a switch that disables the a/c condenser clutch and brings the a/c condenser fan on, even if the a/c is off.  Is it possible that the coolant temp rises enough to trigger that?  It would be a fairly easy "defeat" if that is what is happening.

If you mean the fan motor is weak... pull out your cabin air filters. I’ve had 3 and every one had leaves and acorns almost filling the box. I rigged up a short piece of heater hose on the shop vac and got most of it out and pulled the filters. Amazing difference.

If you mean the fan motor is weak... pull out your cabin air filters. I’ve had 3 and every one had leaves and acorns almost filling the box. I rigged up a short piece of heater hose on the shop vac and got most of it out and pulled the filters. Amazing difference.

Seems to blow enough air.  By weak I meant that it just won't cool the interior down much when it is really  hot outside. Sorry for the confusion.  I will clean out the air box as you suggested though.  I don't think there is a filter  in the '06 Tracker.  Ill check.

I disassembled a Sidekick Sport a few years ago and the expansion coil was mostly covered in debris. It couldn't possibly cool as effectively as it did new. It is painfully difficult to remove and inspect. My current Sidekick is no longer cooling well. It seems to be the expansion valve, which is also painfully difficult to remove.