I even hesitate to call it a problem, because it hasn't really failed me, especially on very hot days, but...

One day a few months ago I was driving through a sparsely-populated area, one might even say, down country roads, winding and sometimes surrounded by trees, when it failed. I had to open the windows because it became rather uncomfortable in the car.

A few weeks ago, returning from a long trip via the interstate, it failed briefly but came back after a little while.

Not exactly sure what caused the problem either time. I did try charging the system before the long trip though. The gauge on top of the can was already in the green. The system hasn't failed me since then but I haven't really taken any unusual trips since then, either.

 

First you need to define "failed"...

 

Becomes warm, loses the ability to cool for a period of time. Warm(er) air comes out the vents, even at MAX COOL, coldest setting, high fan. It's definitely not nor ever was HOT air, maybe closer to the temp of air when you have VENT selected.

If I had to guess I'd say the compressor stopped working temporarily during those times.

 

Does your 2003 have an "Auto" setting on the fan switch and temps (20-25-30), on the heat setting?

If it does then it could also be in the temp control sensors and circuitry...

 

Check the compressor clutch gap.

 

I don't see anything indicating an Auto setting, seems to be all manual.

 

Ok then that likely does limit the problem to the a/c side, assuming correct gas charge and it is cold when it works I think that pretty much limits it to the compressor, its wiring and relay...as commented check the clutch gap but I'm not that experienced within the a/c to comment further...