Engine cooling fan not coming on

[Swanepga]

I have a 2005 ford fiesta 1.6 duratec.... The engine cooling fan does not come on.... Replaced temperature switch.... Checked relay and fuses all ok...... What can be wrong

 

[Handy Andy]

Were you able to short the terminals of the relay to make the Fan turn on?

Fan uses a 15 or 20 amp fuse - if the original fuse was ok, was the relay tested?

It's a 2005 - 2022 - 17 years - better check the wiring.

 

[mart53]

Have a 1.4 Fiesta with a similar problem. Could you tell me how you sorted it- assuming you did!! Martyn

 

[scotman]

The best way to confirm the cooling fan is not functional is to jumper the relay to confirm if it works or not.

 

[Handy Andy]

The Relay from the fuse box, sends a wire to the PCM to complete a circuit that GROUNDS (sends power thru) the COIL side of the relay - the coil energizes and the contacts it has inside the Relay, then complete ANOTHER circuit by letting the Circuit GROUND thru it and the fan - so the circuit is completed and the FAN runs - for as long as the Relay is energized by the PCM telling the Relays' coil to do so.

Here's the Problem....

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There are at LEAST 3 variants of the "Cooling Fan" circuit used in Fiesta or ANY Ford model - so the PCM uses AT LEAST 4 different points to turn on and off the coils to those relays that control those Fans - and in some variants a DROPPING resistor is in series with one relay that powers the FAN to slow it down as a LOW-SPEED fan setting to make it efficient and quieter and only kicks into high speed FAN (full Speed) as demands are made to keep the system cool.

To help you - you'll need to find the RELAY the runs the fan, it will have a circuit imprinted on it (I hope) so you can review the Pin out and which pins control what - so you can find the FAN contacts - jumper them, and see if the FAN works - if that test passes - look on the RELAY for the Squiggle box and it's lines showing which pins are used - there would be two.

The TVS means a Transient Voltage Suppressor (Diode) - a key ingredient to keep the coil of the Relay from damaging the PCM if the relay is ever "overpowered" by a voltage spike - if the event were to occur, that can damage the PCM!

So this may mean a trip to the shop for a diagnosis. The PCM can be damaged and may need to be replaced.

This also goes back to properly functioning charging system, a loose battery cable or a bad jump start done years ago can leave behind damage that accrues into a failed PCM caused by poor voltage regulation. So keep after your battery and maintain good connections that you can get access to - as you can - to help reduce this and prolong the life of the car.