Cooling Fan Relay Wiring Diagram: Fan Not Working or Engine Overheating

A cooling fan that never turns on is not the same as a fan that runs only with the A/C, runs all the time, or runs at one speed. The first question is whether the engine computer is commanding fan operation.

Use the wiring diagram to identify the temperature input, PCM or fan module command, relay control side, relay load side, fan motor feed, and ground path before replacing the fan motor.

A relay can click without delivering current to the fan. The control side may be good while the contact side, fuse feed, fan motor, connector, or ground path is still faulty.

Check power at the relay feed, command at the coil, output to the motor, and voltage drop on the ground while the fan is commanded on. The diagram tells you which terminal should do each job.

Many vehicles use the radiator fan for both engine cooling and A/C condenser airflow. A pressure sensor, A/C request, or HVAC module can affect when the fan runs.

If the fan works only with A/C or only with engine heat, compare the two command paths in the wiring diagram instead of assuming the motor is bad.

Some vehicles use low-speed and high-speed relays. Others use a resistor, fan control module, or pulse-width modulation. The testing path changes with the design.

The exact year, make, model, and system diagram prevents wrong relay jumping and helps identify whether the fault is in the fan, module, relay box, or control input.