[slowmover]

You can also "up" the performance of an A/C system by bypassing the heater core, even if for just the summer months. Where I live an A/C system in a car is not optional, and it runs 9-10 months full-time (at least at mid-day). High humidity is a bear to condition.

Proper -- legal -- window tint is of benefit.

Use a windshield cover (interior; keep the vehicle windshield pointed away from the sun when parked year round; OEM-quality); crack the windows if security allows when parked (finger-tip width), and run MAX A/C after opening windows a bit as you get rolling to exhaust hot air, then closing them.

It will take a while to cool more than just the air as the A/C needs time to cool the "furniture" of the vehicle. I say "get it to that point" before switching to FRESH air. (The drier the climate the sooner this will be; humidity takes time to overcome). One can back off the TEMP setting a click or two to reduce compressor cycling, but maintain MAX until nearly blue-knuckled (your clothing is long past dried). This really is the earliest point to change over. Not chilled clothing, but dried & chilled.

FRESH plus an increased temp will take care of it the rest of the day (or until shutoff). It is also when I switch over to combined foot & head airflow (what we used to call the "highway" position). One can -- from hereon -- experiment with further reductions in, first, temp, and second, airflow.

I point most all vents as high as possible, and towards the back of the cabin. This produces the most rapid cooldown, and maintains even sorting (layering) prior to exhaust.

I use a thermometer to measure outlet temps, and this also informs me of how the system is doing as a check against the way I feel (a bit more consistency in operation).

All of this assumes: clean condenser (rare), clean evaporator (look into this, it is vital), proper refrigerant charge (rare), and proper weather seal function (as well as cabin exhaust function). The best long-term operation of the HVAC system trumps a tenth or two. Do some investigating. There are enthusiast sites with the occasionally well-informed membership (rare) and a couple of sites dedicated to mobile HVAC with service techs and others online (better). Some systems vent refrigerant more often than they should, and some leaks are harder to diagnose/find than others. Obviously, living in TX, AZ, and FL one finds the better, more experienced shops.

Another DIY is a separate condenser fan to "up" performance and to keep the compressor from cycling as often. Head pressure can be quite high at startup (hard on whole system).

Today's compressors are nothing in power draw compared to what we used to see on late 1950's thru mid-1970's cars (and why small cars simply didn't have A/C available). On the other hand you could hang meat in those cabins . . none of this bull about 20F below ambient stuff! 119F full sun Las Vegas heat and 62F in the car, ha!

A garaged car, or one under cover, always has better HVAC operation than one exposed to all elements. I pay for covered parking (not just for this benefit).

.