I drove my son's '99 Elentra in stop and go traffic, ambient temperature
around 103, and I looked down to see the temperature guage about 1 - 2 mm
from the red zone.  I turned OFF the A/C and reduced all electrical draw.
The temp slowly went down... and got better as the traffic opened up. I was
then able to turn the A/C back on. The engine temperature was in the normal
range by the time I was getting close to home.

The weather cooled down but after dinner I went out into the driveway,
started the car, put on the parking brake, and put it in reverse (labored
idle) with the A/C ON.  The 2nd fan never started - and the temperature
guage registered "normal".

1) When should that other fan turn ON?
2) What is the simplest and easiest way to cheaply determine if the fan is
bad (or wiring bad)?

The car runs great other than this one incident... oh, and two weeks ago, on
a similarly hot day, my son reported that the A/C cut out while they were
idling in a parking lot waiting for someone.  He turned OFF the car and
called me. I thought at the time that it was a thermal or pressure relay,
maybe keeping the A/C from overloading... he hadn't looked at the engine
temperature gauge... maybe the car was overheating then too... don't know...
it started back up and was fine immediately thereafter.

No other odd symptoms other than a slight smell of burning insulation when
it was on recirculate (so I looked to see if the intake on the floor was
blocked.... it was not that I could see).

TIA.