Fan will not come on when heat is turned on, no matter how high the temperature is set.

if the scan tool ECT sensors show 180f to 200f it is not overheating
what are you talking about.
blower dash fan.
engine RAD fans < guess only this.
or front AC condenser fans.
overheats parked
overheats driving yes or now fast?
oveheats only AC on, none of this told an matters HUGE.
learn to use a scan tool?
you can not fix any modern car lacking one. $100 buy one.
here are the proofs of over heating. al or most.!!!
dash gauge pegs, see that can be coolant low, easy no>?
scan ECT shows temps way over 200F, 265 is boiling point.
coolant on the ground AF 50% green,yellow orange pink what eva.
coolant on the passengers toes(foot well heater core leaks)
coolant in oil pan , and dip stick end drips, chocolate milk.
engine pings, or under load (hills) dont let it. pings is too hot. or dead EGR.
huge engine power loss from ping. (and lots more)
engine guts make huge nasty metallic sounds. bad that. check oil levels.
dash gauge engine heat PEGs , can mean overheating.
dash gauge tad high is normal. z(operators guide said so)

the service manual tells you clear as day what temps trip the fans on if you just RTM/ 214 to 220f , if ECT show that the fans run in that range and lacking a scan tool you will NEVER KNOW IT.
'the dash gauges is NOT and instrument it is a just a crude, toy gauge, the ECT is what matters period. or IR thermal gun pointed to thermostat housing then to top and bottom RAD tanks,


this magic tool and skills I can find dead RAD tubes in 1min flat
love mine, Have 2.

shows 170 here, or 180f if drive 5 miles. your car is 200f stat
a parting shot
no 19 year old thermostat run that long.
the top usa maker claims a 7 year design life
I bet yours is bad. as the wax pellet ages in it ,it shrinks and the TEMPS go way way too high, or are sluggish.
seen it vast times and is frankly normal service.

Your heater sensis the temperature in the cab and turns down the heat. adjust you climate control to med high or so. temp not fan it can still be set to high. Check your owners manual.

Mike.

Mike

If you have a fan that has different speed settings (1234, or low med high etc) and the only one that works is high - then the blower resistor pack has failed. If you have a climate control unit (where you just pick a temp you want) then the fan is controlled by the heating system and it sets fan speed. If you have climate control style try lowering the temp to a lower setting (current temp in vehicle) and see if fan slows down. If not then climate control unit or fan resistor bad. If dial type and you get nothing on lower settings (only high works like mentioned above) you need to change blower resistor. It is located under dash near the fan itself. Look for small unit bolted in duct near fan with wire plug going to it.

I would start with the rear blower motor resistor, the resistor is what controls the speed of the fan, the resistor is located in the rear heater box near the blower, you will need to remove the right rear side panel to access the heater box. start with that

change the thermostat, sounds like it could stuck open and wont allow the engine reach operating temp, also test the constant control relay module located to the right of the battery as your facing the front of the car, also test coolant temp switch it might be defective and producing a high voltage that would cause the fans to constantly operate no matter the temp. Hope this helps

how cold is that in real temperature scales like centigrade please ,watch ice road truckers and learn --- put a piece of cardboard in front of the rad to block the air flow ,that will do it

The Heater box resister is bad. Simple replacement. Also when disconnect the connector look for melting. This is common for the Jeep

Your Heater Power control module is bad I just had the same problem you can find it right behind the glove box it is mounted in the heater duct very easy to fix 2 screws and it is out and cost is about 150.00 at the dealer it is a dealer only part.

change the fans relay or ac\clutch relay

Fifteen minutes! you have bigger problems than only the fans the fans are controlled by a thermo switch that is heated by the coolant, If you have no coolant the sensor cannot activate But fifteen minutes seems like you may have a headgasket problem and steam cannot heat the coolant sensor.OperationNotesThe electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the Powertrain Control Module (PCM) . The PCM turns the cooling fan ON by grounding the coil of the cooling fan relays when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.

Power for the cooling fan motors are supplied through Maxifuses(R). The cooling fan relays are energized when current flows from the fuses in the Underhood Accessory Wiring Junction Block, and through the relay coils to ground through the PCM. The Coolant Fan 1 Relay Control Circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The Coolant Fan 1 Relay Control Circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.

IMPORTANT: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. Perform the A Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.

For more information regarding the Charging System, refer to Charging System Description , and Charging System Circuit Description in Starting and Charging.

If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 Cooling Fan Relay 1 Control Circuit should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 Cooling Fan Relay 2 Control Circuit should set. A problem with the ECT sensor should set DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage, DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage, DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage, DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Electric Cooling Fan Diagnosis.

For more information regarding the Cooling System refer to Engine Cooling Fan Description - Electric, and Cooling System Description in Cooling System.


Here is the electrical schematic and how it all is suppose to work,
If you need any further help please contact me Thank you,Randy If you find this information helpful please give me a good rating

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