Fan is not coming on to cool engine - 1997 Chevrolet Lumina

The engine cooling fan is located on the front of the engine between the radiator and the engine block. You do not feel it through the ac vents.

the air con fan comes on with the air con switch. the engine cooling fan comes on when the engine temp. censer reaches operation temp. most times the air through the radiator when driving is enough to keep the censer cool and the fan not working if you stop at lights for any length of time it will come on.

coolant temp sensor tells the computer how hot or cold the engine is so it can regulate the idle and fuel mixture, when it fails there usually is no cooling fan and you will have trouble starting the engine and keeping it running.

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.

If the fan not turning on when car engine getting hot,then car will notice overheating.Click this link below for troubleshooting:---http://technoanswers.blogspot.in/2012/02/car-running-hot.html--------To know how engine cooling system works ,click the link below :----Engine cooling components working?

http://repairhelpcenter.blogspot.com/2011/11/engine-cooling-components-working.html

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How does Vehicles Engine cooling system works? http://repairhelpcenter.blogspot.com/2011/11/how-does-vehicles-engine-cooling-system.html
------------How to Replace Engine cooling Fan:-- http://repairhelpcenter.blogspot.com/2011/11/how-to-replace-engine-cooling-fan-on.html
-----------Replace Fan Relay but still Radiator cooling fans not working? http://schematicsdiagram.blogspot.com/2011/12/replace-fan-relay-but-still-radiator.html
----------DIC says "COOLING FAN FAULT"? http://schematicsdiagram.blogspot.com/2011/12/dic-says-cooling-fan-fault.html
---------Where Is Radiator Fan relay and Fuse Located?

http://schematicsdiagram.blogspot.com/2011/12/where-is-radiator-fan-relay-and-fuse.html

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This will help.

Thanks.

Check all fuses first. if the fuses are okay, disconnect the engine cooling fan connector and using jumper wires, connect the fan motor directly to the battery and ground. If the fan still doesn't work, replace it. If the fan does work, its relay may be faulty. Check in the engine compartment fuse box for the cooling fan relays. Try switching the cooling fan relays and see if the engine fan comes on and the a/c condensor fan stops working. If so, the engine cooling fan relay is faulty. If the engine fan still doesn't come on with a good relay, then check the engine temperature switch located at the passenger end of the front cylinder head. It is supposed to switch (have continuity) when the engine temperature reaches 205 deg F. You can remove the switch and put it in a pot of close to boiling water (212 deg F). If it doesn't have continuity at that temperature, it is defective.

automatically. even if the motor is off.

it will come on but only when the engine is very hot and the first fan cant cool it down that fast,, its turned on by a difrent heat censor so the engine needs to be realy hot to set the second fan running and it may even then only run for 30 seconds till the engine temp drops off,,, as long as the car is running in the normal heat range dont worry about it,,, if its cooking way up in the red,,,,,now worry about it,,fast too,,

The Cooling fan is Wired in in such a way so as to Automaticly Turn on Cooling Fan If the A/C is Switched ON. If "WITHOUT the A/C on" The Cooling Fan Doen NOT come ON Untill Engine. is @ 210-230 Degrees
There IS a Problem with the Engine COOLING SYSTEM, A Faulty Coolant Temp Sensor Will Cause this Problem. The Cooling fan is Also A Candidate For Testing.

Answering your Quwstion YES The Engine Coolant Temperture Sensor Tells the ECM What the TEMP Is and the ECM Grounds the Cooling FAN Relay to Turn ON Cooling FAN. Temp Sensor is the Usual Culpret, BUT Relay Comes in a CLOSE Second. Hope this Helps !!!