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Cooling fan manual switch install


You are at the race track or drag strip, pushing into the limits of your Mustangs engine, suddenly you see the Water temp gauge needle start to raise dangerously, should you stop??

Not with this fine tip.


The fan is controlled by the PCM and/or the Constant Control Relay Module (CCRM), when the EEC detects certain temperatures it will switch the fan to either it's low or high speed settings. The A/C will turn the fan to high speed when it is set to max.

But how can you bypass both the EEC and CCRM and install a manual switch to control the fan operation?

First you will have to disconnect the NEGATIVE battery terminal and locate the CCRM and a pin on its connector.

The CCRM module is located LEFT (you looking at engine) of the radiator reservoir/overfill bottle.

Now that you located the CCRM, remove the connector, you will need a 6mm socket to detach the connector from the CCRM housing.

5.0 models:

Locate PIN / WIRE #17 (GREEN with PURPLE stripe) on the connector , it should be easy to spot, the connector has numbers for each pin.



Hook into pin#46 on the PCM, that is located behind the passenger side kickpanel. Once you tie into that pin all you do is run it to the toggle switch, and run the other side of the switch to ground.

Next you will have to TAP a wire to #17, don't CUT THE #17 WIRE !!!, you could use a scotchlock connector to tap into it, OR REMOVE about 2 mm of insulation and wrap your wire to #17.

Get a second wire and connect it to a GOOD GROUND, now run BOTH wires into the cockpit through the firewall, choose a spot to install the SWITCH, connect the wires to each of the 2 switch terminals.

Now is test time, turn key to ON, and flip the switch......READY !!!


The fan switch will NOT change the fan operation under normal circumstances, which means that when the switch is set to OFF, normal fan behavior will be preserved.

If switched ON, the Fan will operate CONSTANTLY at HIGH SPEED no matter how is the coolant temperature or if the air Conditioning is set to ON Normal/ ON MAX.

Since the SWITCH attaches to the high speed relay negative pin in the CCRM, no HARM could be done to either the CCRM or PCM, this way the RELAY is forced to close the circuit, just as when the A/C is on the MAX position.

Adverse effects of using the FAN would be:

  • Reduced battery life

  • Increase chance of drained battery when using with faulty alternator or maybe while using hi-powered amplifiers or underdrive pulleys.

  • Reduced fan motor life

Article by: GTRaptor Profile | E-Mail

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