Radiator cooling fan is not running

If you are referring to the fans both running when the A/C is on, if the high side of the system (condense temp) does not get to a certain temp calling for the second fan, it will not turn on. The single fan running without A/C would normally be for cooling the engine temp (antifreeze).

If you you are running it in Defrost the A/C will turn on to dry the air thus turning on the Rad fan also check to see if your A/C switch is turned on.

Couple of reasons. You may need to have the Radiator backflushed to remove sediment. You also have an Electric cooling fan which may be malfunctioning. They (fans) often have more than 1 speed and high speed may be broken so it can not keep up with extreme heat.

Some fans use more than 1 relay to switch the fans and the second stage relay may be bad.

Overall, the A/C coil is placed in front of the Radiator and depends on airflow to function. This makes the air available to the Radiator much hotter so the Radiator is having a hard time cooling the engine. The Electric radiator fans kick up the airflow to help both systems out.

A dirty radiator, old antifreeze, etc. can affect performance.

I hope my solution is helpful. Radiator shops can service most Brands.

is the cooling fan coming on?Its the fan behind the radiator.If not can be a bad cooling fan motor or coolant fan turn on switch

Hello: Check the radiator cooling fan. With engine running and A/C on open hood look down on the back-side of the grill, that's where the cooling fan is. It should be running, if not check the fuses, cooling fan relays/module if they are ok then you may have a cooling fan motor failure. You can use jumper cables to hot wire the fan motor to see if it runs.

YOUR AIR CONDITIONER PUT LOAD ON ENGINE CHECK TO MAKE SURE RADIATOR COOLING FAN RUNNING BECAUSE IT HELPS TO KEEP THE ENGINE COOL AND AC CONDENSOR COOL FAN NEED TO BE RUNNING IF NOT CHECK COOLING FAN FUSE OR RELAY.

Hi and welcome to FixYa I am Kelly.
You have 2 fans because one is the temperature controlled radiator fan that only runs when the engine water temp is above 160 deg. F. The water termperature controlled fan can run even with the ignition key OFF should the Engine water temp be too hot.
The 2nd fan is for your Air-Conditioner that should run when the cabin temp is set low enough for the Air-Conditioner compressor to run. This fan should run anytime the Air-Conditoner is switched on.
If your experiencing engine over heat problems when driving slow or sitting idle most likely the fan switch that is switched on by water temperature has failed. The fan switch controls a fan relay and if the relay fails the fan will not run. In this particular model there is a cooling fan module that controls the fan.

Read this link but DO NOT click on any links from that webpage: (They do not work)
http://www.fixautopartz.com/2009/03/20/2003-mitsubishi-outlander-engine-cooling-system

Thanks for choosing FixYa,
Kelly

one fan is dedicated to the cooling and comes on when it needs to cool the coolant in the radiator, while the other fan is used when you run the air conditioner it helps cool the radiator when you add the workload of cooling the inside of the car. they work seperate from each other, while actually working together.

IF YOU GOT ELECTRIC COOLING FAN MAKE SURE YOU GOT IT HOOKED UP.IF NOT FANS DONT RUN IN WHICH IT COOLS REFRIGERANT IN CONDENSOR.AIR CONDITIONER NOT GOING TO PUT OUT COLD.

Check the cooling fan switch. It appears your auxiliary electric cooling fan isn't going on when at idle. and engine temp increases. While you are driving, air is being rammed thru your radiator as you cruise along, so it isn't overheating, at idle, that isn't happening, and the fan should go on as the temp goes up. When the ac is switched on, the fan is being signaled to operate due to the heavy ac load on the cooling system.