Why does it overheat with the A/C fan on?

so only the gauge tells you that. and not other real symptoms of
overhreating
coolant on the ground
lost engine power
engine pings hard, for sure under load.
scan PCM DTC set for ovehreating or ECT or Thermostat errors
PCM scan shows ECT live data ,200F, not must above.
at 6am, or daybreak, not used, cold engine, rad Cap off (new one is best cap) and RAD is full up to the top.??????????
50% AFR coolant check that is 50% with the cheap tool.>?
see oil floating in rad cap off hole or carbon dust>?
dip stick pulled on engine and oil looks like chocolate milk (panic)
compression good and spec, on all cylinders. (a test)
10 year old thermostats and rad caps are a bad idea.
does it overheat moving fast for sure 50mph, ???????
or only parked, at red light and all fans dead. oops.

the AC also has a fan upfront and must not be dead.
all fans must work. for sure at red lights.
moving the car fast , it must not overheat.
is the RAD side bottle a wreck. it must be working no bad tubes

Could be but I would get it checked. There could be an air pocket in the cooling system, sticking thermostat, fans not working or water pump not pumping efficiently. Overheating can cause blow headgaskets, cracked head or blown engine all of which are very expensive to fix.

the ac fan starts as soon as the ac is switched on
the fan is provide cooling of the condenser before the radiator to prevent high head pressures in the ac compressor
it is the fan at the front of the car mand does not affect engine temp
there is a radiator fan between the engine and the radiator that will not start until the coolant temperature reaches a set temp at which point the ECM switches that fan on
if that fan is not working when the engine is hot , check for fan, coolant temperature sensor switch , fan relay, fuses or problem ECM

210-230 degrees usually .

if engine at long stand still,the engine temperature will rise about 190 degrees the cooling fan suppose to automaticaly turn on when coolant temperature sensor get hot it cause its resistance decrease causing pcm to send power to coolant fan relays and cooling fans, when you turn on AC the cooling fans suppose to turn on to cool down AC CONDENSOR, IF NOT AC WONT WORK COOLING FAN COOLS DOWN REFRIGERANT SO IT CAN RECYCLE THROUGH THE SYSTEM AGAIN.your cooling is suppose to turn on when engine at a sit still if vechicle not moving as coolant temperature rises at a set point the cooling fans will turn on cool down engine.cooling fans dont turn on when you first cold stsrt vechicle unless you have AC SWITCH ON.if cooling fans dont turn on when vechicle at a long stand still or moving along slow traffic.if coolant temperature sensor been replaced and fuses and relays okay have dealership check see if pcm driver circuit working faulty pcm will cause cooling fans not to turn on.

Your radiator fan is probably failed. Pop open hood, watch temp rise, once past "normal " level teh fan should turn on. If not, you need to trouble shoot the rad fan. There should be heavy duty fuses and relays under the hood in an electrical distribution box. You should consult the owners manual or chart on the box lid. Of course the fan maybe bad itself. You can also try - turn on the AC, this will activate the 2nd (booster) fan, and should help prevent serious overheating but wont fix the underlying problem.
Good luck

REPLACE THERMOSTAT.ITS STICKING CLOSE TO KEEP COOLANT FROM CIRCULATING THROUGH ENGINE AND RADIATOR. THE FANS SHOULD COME ON WHEN VECHICLE SETTING AT A LONG IDLE.THE COOLANT TEMPERATURE SENSOR GET TO CERTAIN TEMPERATURE WHICH WILL COMPLETE CIRCUIT PCM SEND POWER TO COOLANT SENSOR THEN TO COOLANT FANS RELAYS AND FANS.IF VECHICLE OVER HEATING WHILE MOVING THERMOSTAT FAULTY.IF YOU TURN AC AND COOLANT FANS DONT RUN CHECK COOLANT FANS FUSE AND RELAY.IF COOLING FANS DONT TURN ON WITH AIR CONDITIONER ON EITHER COOLANT TEMPERATURE SENSOR FAULTY OR PCM FAULTY.IF ALL LOOKS GOOD.IF ENGINE OIL LOOKS LIKE MILK SHAKE.YOU HAVE BLOWN HEAD GASKET.

yes the head gaskets leaking on modern aluminum head engines is all to common. never overheat them, if they start to get hot shut it down and find out why, it can of course be the fans and plugged radiators or faulty thermostats but sounds like in your case the head gasket is leaking and combustion gas is entering the cooling system and this causes an overheat

Sounds like either you are low on coolant or the cooling fan isn't working. With engine cool remove radiator cap and check coolant level, top off if necessary. If full start engine and turn on A/C full blast, full cold the cooling fan should come on almost instantly, unless there are two individual cooling fans in which case only one may turn on. If no fans turn on check all fuses whether related to fan or not. If all fuses fine try swapping relays around, they are usually all the same size/style. If fan still doen't work you have either an open positve or ground side of the circuit, Which will require wiring schematics and a multimeter. If coolant full and fan/s turn on and engine still overheats you'll need a new thermostat installed.

I just had my coolant flushed and my radiator cooling fan replaced. The car was slightly overheating and would "gargle" in the coolant bowl after I turned the engine off. It turned out to be the radiator was clogged up on one side.

I went full tilt and replaced the radiator, water pump, thermostat, radiator cap and timing belt. I have 85,000 miles on the car and it was about time to do these things anyway. It is running like a new car now.