Nc24 fan not running

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Hi all
Nc24 won’t run after 1sr check in 4 years.
Temp gauge works
Fan works when shorted to the frame.
Was running the bike the temp was getting close to the red so didn’t want to push it.
When I had the bike apart I wanted to test the brass unit switch but seems to be really tight and didn’t want to
Damage the rad
Anyone offer when the fan normally kicks in ? I can’t check temp so just from the gauge before I try and replace
Thanks
Chris
Can’t upload a pic to show gauge?

[CB1pod70]

This is a common problem. Does the fan work when you disconnect the lead from the brass sensor and short it on the radiator? If it does then it is the sensor that's failed. If it doesn't then it is probably corrosion on the earth leads which are normally mounted to the top bolt holding the fan assembly to the radiator.
The sensor doesn't normally seize in but the bolts holding the fan on do, so expect to use some heat & penetrating fluid if necessary. Last time I looked Wemoto were selling the sensor for around £25

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Thanks
I bought a replacement unit tried in boiling water and had continuity
Great fitted to bike.
Got into red and no fan, very annoyed.
The fan works when shorted to frame.
Had continuity on the thermistor. All I can think is that the -ve path has high resistance?
I did paint the rad so will scrape the connections, thisBike is really trying my patience
Chris

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To the point I am starting to hate the bike after working on a refurb off and on for a year

[cbr400rrn]

Don't get disheartened with it just put it away for a week then go back to it. In the meantime think/research what the problem could be, you will find others have had the same trouble as yourself.

Paint on the terminals will stop an earth path, finish what you started and then when it's completed (they are old bikes so will all have problems that need rectifying) stand back, crack open a beer and smile at just what you have achieved but it can become addictive.