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Ford Mustang Cooling Fan Sensor

Q. 1993 Ford Mustang 4 cylinder. Where is the cooling fan sensor located? I've got one of the two problems, fan or the sensor but I don't have a Haynes book on it,and I can't tell where the sensor is. It's not on the top of the radiator. Thanks a million if you can help. Cool weather down south is okay, but I just found out the fan has faulted during one of our warm days last week.

Thanks again,
Walt
Charleston, SC

Ford Mustang Cooling Fan Sensor

A. There is no cooling fan sensor per se, the cooling fan is controlled by the Electronic Control Module (ECM) through the Integrated Relay Control Module (IRCM).

The ECM monitors coolant temperature, vehicle speed, and air conditioning status to determine if cooling fan operation is required. When the ECM determines a need for cooling fan operation, it sends a signal to the IRCM to run the fan at the required speed.

Basically they took all the relays and made them one unit. So instead of having to replace a $10.00 relay, you now have to replace a $200.00 some odd dollar module.

Here's how to troubleshoot it.

  1. Check power supply to Integrated Relay Control Module (IRCM ).
  • Key off. Disconnect IRCM.
  • Measure voltage between pins 3 and 4 at the IRCM vehicle harness connector and battery negative post.
  • Is each voltage greater than 10.5 volts?
YES: Go to step 2.
NO: Service open in the battery power circuit, and retest system.
  1. Check fan motor operation.
  • With the key off and the IRCM disconnected, jumper pin 1 to pin 3 at the IRCM vehicle harness connector.
  • Does the fan run?
YES: Go to step 5.
NO: Go to step 3.
  1. Measure battery voltage supply at the fan (bypassing the IRCM).
  • With the key off, cooling fan and IRCM disconnected, jumper pin 1 to pin 3 at the IRCM vehicle harness connector.
  • Measure voltage at the cooling fan vehicle harness connector between the power and ground pins.
  • Is voltage greater than 8.0 volts?
YES: Replace the fan motor, reconnect the IRCM and retest.
NO: Go to step 4.
  1. Verify the cooling fan ground.
  • With the key off, cooling fan and IRCM disconnected, jumper pin 1 to pin 3 at the IRCM vehicle harness connector.
  • Measure voltage between positive terminal at the cooling fan vehicle harness connector and battery negative post.
  • Is the voltage greater than 8.0 volts?
YES: Service open in the ground circuit to fan. Reconnect all components and retest.
NO: Service open in the power-to-fan circuit from IRCM vehicle harness connector to cooling fan vehicle harness connector. Reconnect all components and retest.
  1. Check fan running mode (low).
  • With the key off, disconnect the processor.
  • Reconnect IRCM, turn the key on with the engine off.
  • Does the fan run?
YES: Go to step 6.
NO: Replace the IRCM. Reconnect and retest.
  1. Check Engine Coolant Temperature (ECT ) sensor.
  • Check engine coolant level.
  • Key off.
  • Install breakout box, with processor connected.
  • Warm engine to operating temperature before taking ECT resistance measurement.
  • Key off. Disconnect ECT sensor and measure the resistance of the sensor.
  • Is the resistance between 1500 ohms and 2000 ohms?
YES: Replace processor, and retest.
NO: Replace the ECT sensor, and retest.

Ford Mustang Cooling Fan Sensor

Additional Information provided courtesy of ALLDATA

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