C3 1.4 HDi Radiator Fan always on !

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eimaj12000
Posts: 4
Joined: 04 May 2010, 12:22

C3 1.4 HDi Radiator Fan always on !

Post by eimaj12000 » 28 Oct 2012, 04:39

Hi,

I have a C3 1.4 HDi (8HX engine) and have a strange problem with the radiator fan. The cooling fan (rad fan) on the car stays on permanently until the battery is flat with ignition on or off ? I've scoured the web for a solution to this but can't seem to find what would cause this. Have run diagnostic with Lexia and picks up no faults with temp sensor etc and shows fan speed to be zero so ECU isn't telling fan to do this ! The instrument panel temp sensor seems to work sensibly and from what I see there is only one coolant sensor on this engine (green one) ?

Also, I notice the radiator has two connectors - one is two wire and supplying 12V all the time (ignition on or off) and the other is three small wires which i take it are signals from ECU to control fan. Now, is it possible that something inside the fan requires repair (is there some kind of diode arrangement perhaps and a diode has blown)? It seems the web is full of experts on the engine, common rail etc. but I have yet to see someone explain how this fan system works - can't seem to find any relays or similar that could be stuck ? A french forum seemed to suggest that the problem was the ecu 'forgetting' about the air con circuit somehow and panicking thus inducing the fan ?

Any help would be great.

[-o< [-o<

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Lighty
Posts: 1100
Joined: 07 Jan 2012, 17:53

Re: C3 1.4 HDi Radiator Fan always on !

Post by Lighty » 28 Oct 2012, 10:44

Assuming you have checked on Lexia that anti boiling stratedgy is not activated, then It is most likely the fan, they have a built in control box next to the motor, and they do fail in this way.

eimaj12000
Posts: 4
Joined: 04 May 2010, 12:22

Re: C3 1.4 HDi Radiator Fan always on !

Post by eimaj12000 » 28 Oct 2012, 15:13

Thanks for your reply Lighty. According to Lexia the fan is off so this leads me to believe that some component has blown between the wires and control to fan now leaving it on permanently. I did read part of a post on a French forum which seemed to be about replacing a diode inside the fan somehow ? Anyway, replacement fan is what I've decided and I'll strip old one when it's off and see if it's repairable as a spare.

Thanks again - very much appreciated.