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Once the engine is warmed up (temperature gauge in normal range), the cooling fans begin operating at high speed and never shut off until ignition turned off. Fans never run after ignition turned off.

Cooling system has been flushed (60/40) and thermostat replaced. Condenser and radiator are clear of bug blockage.

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  • Cars & Trucks Master
  • 1,669 Answers

It sounds like the cooling fan relays are latching on. The contacts are probably partially welded and sticking closed so hard the recoil spring to pull them open again is too weak to do so. Change the relay(s).

Posted on Jan 21, 2013

  • Michael Noel Mar 26, 2013

    Ended up taking vehicle to dealer for a recall and while there asked them to troubleshoot cooling fan issue. They say it is the water pump impellor not moving enough coolant.

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alatimore43
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SOURCE: The cooling system electric fans keep running for over 45 minutes. The engine temp gauge was in the normal range. There is no thermostat in the cooling system, the radiator was warm but not overheatin

there has to be thermostat sensor in the system. this is how the cooling fan is controlled.the water pump may be failing by not pumping enough coolant and causing the fan to run.longer that expected

Posted on Jun 24, 2012

  • 132 Answers

SOURCE: subaru 2000 outback cooling fan never stops

Replace the cooling fan sensor.

Posted on Mar 26, 2009

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Need a wiring diagram of the 2 wires from the temp sending unit that controls the temp gauge and cooling fans on a 99 grand am gt. Need to see where they go They disappear behind the engine


The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay 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 Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans 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. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

Nov 13, 2016 | 1999 Pontiac Grand Am GT

1 Answer

My car 2008 Chevy Uplander warning light came on stating A/C shut off for engine protection. My question exactly as 1posted 2011. Gauge not Reading. Fan running continuously. Doesn't seem hot.


What gauge not reading , Temperature ? you posted back in 2011 ? You did feel you should take it to the repair shop ? You need to take this to a ASE certified repair facility ! This is a complex electronically controlled cooling system , Three relay's controlled by the ECM -engine control module turn the fans on in two different speeds ! There could be DTC'S diagnostic trouble codes stored in the ECM, HVAC module , BCM !
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the low speed fan relay, which is the Fan 1 Relay. Voltage is applied directly to the left cooling fan through the switch side of the low speed fan relay. The right fan is connected in series to the left fan through the de-energized Series/Parallel relay, which is Fan 2 Relay, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the Series/Parallel relay, and the high speed fan relay, which is the Fan 3 Relay. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed fan relay and ground through the Series/Parallel relay.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.
One of the relays could be stuck on ! An for the gauge you have to have it removed an fixed , there is a stepper motor behind the gauge needle an they go bad ! Or replace the instrument cluster !

May 14, 2015 | Cars & Trucks

2 Answers

Overheating


That is normal cooling fan operation. the fans are computer controlled and not turned on until the engine reaches the pre programmed temperature, that is about 185-195F

Jan 03, 2014 | 1998 Chevrolet Lumina

1 Answer

My 2006 ford f250 6.0 litre powerstroke has been showing that it is over heating and now it takes forever to show when the engine is at normal operating range or even warm at all but once it does the guage...


I think first of all you need to verify that it is really overheating and isn't a sensor that has become faulty and is sending false information to the management computer that these days will drive the cooling fan, the temp gauge and any alarms.
An obd scanner should show a similar coolant temp and air temp when the engine is cold and then register a fairly smooth increase after starting until it drops when the thermostat opens and begins to climb again until working temperature is reached and the cooling fan begins to cycle (if electric).

A failure to register and then suddenly jump could be a faulty sensor but could also be indicative of a blocked degassing system or an excessive amount of gas in the cooling system.

It is important to observe the engine during warmup and keep monitoring the heat of various hoses, the thermostat operation and so forth.

Jun 17, 2017 | 2006 Ford F-250 Super Duty

1 Answer

2009 Jeep Wrangler Sahara Unlimited, overheats while driving in off-road conditions (Sand). Dealer has checked for any leaks but everythign seems fine. The 4WD Shifter liankage has been replaced twice....


Your cooling system works by getting air flow over the radiator and good circulation of coolant in the radiator as well as other areas of the motor.
The fan for your radiaror is electric, but it is designed to run at different speeds depending on conditions. First, I would verify that the fan DOES run. Sitting in the driveway with the engine at operating temperature, turn the A/C on and see if the fan speed increases right away or increases after running for 10 minutes. It should have a higher pitched sound. Look at the temperature gauge again and see if it is still at operating temperature. If the temperature continues to climb, turn the heater on full blast and watch the temperature gauge, it should drop.
No increase in fan speed means you could have a module problem or other problem related to the fan speed. In your relay box, relay "K11" is the fan relay. The relay box is in the engine compartment. The underside of the cover will identify what relays go for what. Some Jeeps used 2 relays, 1 for low speeds and the other for high fan speeds.The fan and module are replaced as a unit. The PCM (power control module is the brain for the engine management system including the controling of the fan relays. Sometimes the relays are the same and you can swap them with each other to see if there is a change. Note: If the temperature is normal when you are driving down the road, than the cooling system is normal and it is the fan.
Good luck.

Aug 09, 2011 | 2009 Jeep Wrangler

1 Answer

05 Silverado, overheats when in 4-wheel drive under strain. Fixed once(so I thought) by replacing the water pump and thermostat. Happened a few months later. Again, 4-wheel, under strain. Wound up...


Instrument cluster - GM had problems with a part inside the cluster , Stepper motor , These faulty step motors caused the gauges to act erratically . 2003 to 2006 ! ALL GM vehicles . Just replaced a cavalier instrument cluster for what customer thought was a over heating problem .The fans come on low speed when engine temp. reaches 220 degress
The PCM commands the low speed cooling fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 104.25°C (220°F).
• A/C refrigerant pressure exceeds 1447 kPa (210 psi).
• After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 101°C (214°F) the low speed fans will run for a minimum of 60 seconds After 60 seconds, if the coolant temperature drops below 101°C (214°F) the fans will shut OFF. The fans will automatically shut OFF after 3 min. regardless of coolant temperature.
The PCM commands the high speed fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 107.2°C (225°F).
• A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
• When certain DTCs set.
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed if required. This insures idle stability by preventing the fans from cycling between high and low speed.

Mar 31, 2017 | 2005 Chevrolet Silverado

1 Answer

My heater blows warm air when fan on low then when you turn the fan on high it gets cold.


This indicates that enough hot water isn't getting from the engine into the heater core at a fast enough pace to keep up with the increased demand when you have the fan on higher speeds, and that the system is restricted. If your temperature gauge is indicating the engine is at normal operating temp. or you can tell by the general temperature of the engine, then more than likely, you'll need to have the entire system cooling system tested & flushed good luck

Jan 29, 2010 | 1997 Chevrolet Venture

1 Answer

Cooling fans in op until engine is shut down . At idle, in traffic, temp gets high, hen wmoving, temp goes back to normal. When I shut down the engine the fans start to run as they are supposed to when the...


Check out clarks-garage.com he has a complete troubleshooting guide for your cooling system along with a schematic. In short, check the low speed resistor on the firewall. Should be around one ohm.

Oct 10, 2009 | 1985 Porsche 944

1 Answer

Audi A3 2002 model auto - temperature gauge not working


The guage and fan speeds work on independant sensors. If you can remove the plastic engine cover and locate the "sending unit" for the gauge disconnect it and restart the engine. The gauge should remain cold and not move. If this is the case replace the sending unit. This should be a single wire sender located in the waterjacket of the intake manifold look in the area where the upper rad hose enters the intake.

Mar 19, 2009 | 1999 Audi A6

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