Cooling fan not coming on?

s300 and SManager software questions & answers
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Stevieh6
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Cooling fan not coming on?

Post by Stevieh6 » Wed Jun 05, 2019 5:50 am

Hi, my cooling fan doesn’t seem to be coming on when it should, it just keep heating up until the overheating error appears.
So far I’ve replaced the fan switch and tested the relay which is fine. If I Bridge the fan switch connector the fan comes straight on.
When it reaches temperature I notice the fan switch engage making the revs dip a little but no fan..
I’m stumped. Could it be ECU related?

Thanks
Steve

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Spunkster
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Re: Cooling fan not coming on?

Post by Spunkster » Wed Jun 05, 2019 9:53 am

The fan should operate independently of the ECU. There should be a thermo switch which activates a relay to turn on the fan.

Stevieh6
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Re: Cooling fan not coming on?

Post by Stevieh6 » Wed Jun 05, 2019 1:14 pm

For whatever reason it’s not working. I thought maybe it sent the signal to the ecu then the ecu turns the fan on?

I’ve overridden the switch now and set it to engage at 195*f and that seems to be working

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Re: Cooling fan not coming on?

Post by Spunkster » Wed Jun 05, 2019 2:23 pm

The ECU should n ot be relied on for the fan control. You need the thermos switch working incase something happens.

Stevieh6
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Re: Cooling fan not coming on?

Post by Stevieh6 » Thu Jun 20, 2019 12:57 am

The switch does work. It’s brand new and you hear it kick in. But whatever is between that and the fan coming on isn’t working. I can’t find anything about a control unit, it seems that it’s the ecu which is stopping it working

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Re: Cooling fan not coming on?

Post by Spunkster » Thu Jun 20, 2019 9:09 am

You need to look at a factory service manual and look to see how it is wired and check any relays involved.

Stevieh6
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Re: Cooling fan not coming on?

Post by Stevieh6 » Mon Jul 08, 2019 12:55 pm

Why shouldn’t I rely on the ecu anyway? Any reason why it would just stop working?

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Spunkster
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Re: Cooling fan not coming on?

Post by Spunkster » Mon Jul 08, 2019 1:24 pm

It is meant as a backup and you no longer have a backup. It should rely on the thermo switch and the ECU as the backup if that fails.

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