'99 Elentra, when should 2nd cooling fan turn on?

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.

 

I don't recall the fan logic, so it'd take some playing with on your part.

Technically both fans are controlled by the ECM, but one is primarily an
a/c fan and the other is primarily a cooling fan.

Verify with a/c off that one fan operates. That's the cooling fan. I
don't recall whether both fans will operate if the a/c is on and the
coolant hasn't exceeded normal temp.

 

Both fans should be running anytime the air cond is turned on

 

Well, the driver's side fan goes ON/OFF with the A/C... but while it was at
operating temperature, it was not in stop and go traffic kind of hot. The
fan on the passenger side did not come on. Guess I will need to check
fuses, maybe put the fan directly to the battery to test it or something.