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Questions and Answers

Ford Mustang Cooling Fans Always On

Q. I own a 1997 Ford Mustang GT. My problem; the cooling fans turn on seconds after turning on the car. I have been told to check the PCM (what is that) and the relays. I can't seem to figure out where they are located. Can you help me?

Ford Mustang Cooling Fans Always On

A. There are a few possibilities for this problem. There could be a short in the cooling fan circuit, The Constant Control Relay Module (CCRM) could be bad as well as the Powertrain Control Module (PCM). Another good possibility is a bad Coolant Temperature Sensor (CTS). This is what I would check first since it is cheap and easy to just replace.

The CCRM is located on the right inside fender well.

Ford Mustang Cooling Fans Always On

The CTS is located on top of the engine.

Ford Mustang Cooling Fans Always On

The Electronic Engine Control (EEC) system provides optimum control of the engine and transmission through the enhanced capability of the Powertrain Control Module (PCM). The EEC system also has an on-board diagnostics monitoring system, On Board Diagnostics II (OBD II), with features and functions to meet federal regulations on exhaust emissions.

The EEC system has two major divisions: hardware and software. The hardware includes the PCM, Constant Control Relay Module (CCRM) or Variable Load Control Module (VLCM), sensors, switches, actuators, solenoids, and interconnecting terminals. The software in the PCM provides the strategy control for outputs (engine hardware) based on the values of the inputs to the PCM.

The PCM receives information from a variety of sensor and switch inputs. Based on the strategy and calibration stored within the memory chip, the PCM generates the appropriate output. The system is designed to minimize emissions and optimize fuel economy and driveability. The software strategy controls the basic operation of the engine and transmission, provides the OBD II strategy, controls the Malfunction Indicator Lamp (MIL), communicates to the scan tool, New Generation STAR (NGS), etc., via the Data Link Connector (DLC), allows for Flash Electrically Erasable/Programmable Read Only Memory (FEEPROM), provides idle air and fuel trim, and controls Failure Mode Effects Management (FMEM).

The Powertrain Control Module is located behind RH cowl panel.

Ford Mustang Cooling Fans Always On

Keep in mind, however, that if the A/C is on, or the defroster is on, the cooling fans will run regardless of engine temperature.

Additional Information provided courtesy of AllDATA

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© 2005 Vincent T. Ciulla

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