2. Has anyone measured the air temp at the outlet registers? ..................
You are on the right track here for a DIY check of how well your A/C is working.
Using a temperature probe in the air discharge vents is something I've done for decades as a first pass check on whether the refrigeration system is working well.
I usually expect to see around 40 degrees, or maybe low 40's in difficult conditions and perhaps high 30's in easy conditions.
Here in Houston we've had unseasonably cold temperatures lately. I did the "easy conditions" test this morning and measured 35 degrees outlet air temperature in the 2013 C-Max Energi. Conditions were:
car soaked at about 70 degrees, in the garage
outside air temperature in the low 60's
measurement taken in the driver's side center stack outlet with all other outlets closed
measurement taken outside in a light rain with overcast sky
measurement taken after the car and A/C were on for about 5 minutes
thermostat set at "LO"
blower varied between low and high speeds.
As I said, result was outlet air temperature = 35 degrees.
This is the coldest result I have ever seen on any of my cars, and I've been doing the test for decades. Granted, the conditions were very favorable. Nevertheless, I'm impressed
This is one important benchmark. The next test is what it will do in hot conditions.
We will probably have strong sun and temperatures in the 90's within a few days here in Houston. I will test again then and report.
Have you made this measurement on your C-max yet?
You are also on the right track in asking others here to post their experience in hot climates. We had some record hot days in Houston last summer. The C-Max often registered over 100 degrees. It always cooled off from a heat-soaked condition to comfrotable in a few minutes and never struggled to keep the cabin comfortable while motoring in the hot sun.