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Discussion Starter · #1 ·
Trying to sort out a problem with my cooling fan. Had a race last Saturday and car overheated when warming car up as fan had stopped working, was fine last time out.

No fault codes logged and there's volts across the main two cables at the connector to the fan. There's also a small cable in the fan plug but not sure what that does, I assume maybe sends fan running feedback to ECU? Fan blades turn freely by hand.

Is there a separate thermostat that turns the fan on or is it controlled by the controller box on the fan?

Any thoughts on how to test further would be really appreciated as other option is to get a new fan and try that I suppose, but they're not cheap so don't really want to get one unless its broken.

Thanks,

Phill.
 

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I always thought if the thermostat had a fault the ECU would detect the fault and set the cooling fan to run constant at full speed as a safety measure to prevent overheating happening. If it's not coming on at all then maybe the fan itself is fubar. Any way you can take live feed direct from the battery to the fan + terminal to see if that makes it run maybe?
 

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:thumbsup: When ours did this it was traced to a wire in the middle of the loom that had managed to corrode through! Took Jamie at JAM-Sport 2 hours with a test meter to find it! There was no damage to the outer plastic of the wire or the loom in that area but the cable itself had corroded through! The wire was between the engine bay fuse box and the ECU if i remember rightly.
 

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Discussion Starter · #4 ·
Thanks for the thoughts.

Good point re giving the fan 12V direct, I'll give that a go. Suppose it could still then be the fan controller but rules the fan itself out. Do you know where the thermostat is? I guess I could disconnect or short the thermostat (if I can find it) and see if that causes the ECU to turn the fan on.

Dodgy wire is a thought. Gearbox mount went at Donington a few weeks back and gearbox end of engine dropped down onto drive shaft (quite dramatic as while going down craners at 120mph!). Cant see any disconnected connectors or pulled wires but I'll trace it through and see as seems a bit of a coincidence. If Jamie can do it in 2 hours must be a 5 minute job :smile:

Thanks again for the help!
 

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Discussion Starter · #7 ·
Have done some tests on the fan today that seemed to point to a defective fan speed controller but then connecting the fan back up its now working fine.

With the fan disconnected there's 14.15V across the red and black power cables to the fan speed controller. With the engine cold there's 3.17V between the smaller control cable and ground. As the engine warms up the signal voltage changes (temperatures from OBD2 port):

20degC to 100degC: 3.17V

100degC: 3.11V

101degC: 2.88V

102degC: 2.64V

103degC: 1.70V

104degC: 1.35V

Looked therefore that the ECU was changing the control voltage but the fan speed controller wasn't switching the fan on. Interestingly removing relay 14 didn't disconnect the fan, seems that the fan is wired, via a 50amp fuse, directly to the live rail in the fuse box rather than being through a relay so maybe the setup for the RS is slightly different to the schematic.

Tried giving the fan a direct connection to the battery (i.e.. the fan motor after the speed controller module) and fan ran fine and at high speed.

Assumed therefor that as the fan itself was fine and as the ECU was changing the control voltage with temperature the signal from the ECU was fine, so the fan speed control module must have failed, however, on connecting the fan back up it worked again. The fan switches on at 100degC at about half speed and increases in speed as the temperature rises.

Bit of an inconclusive test therefore, possibly somehow disconnecting things has reset the fan speed controller, though not really sure why that would be as when the battery isolator is turned off there's no power to the fan either.

I guess I'll just put the fan back in and see how it goes paying a bit more attention to water temperature than normal.

Thanks again for the help,

Phill.
 

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Excellent feedback Phil. :nice:

Let's hope it was just a little glitch and your problem is solved.
 

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Discussion Starter · #9 ·
Thanks Andy and thanks for all the help with it. In a way would have preferred to have found what the problem was but at least I know what to check if it does it again.

Now just got to get the sheared exhaust bolt out of the turbo and replace the right hand drive shaft and ready for the next race :thumbsup:
 
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