Fan full speed from start-up... Help?

[2retro]

I know this has been asked before but I can't find the post (or crucially the solution!). Basically, as the title says - the fan comes on full speed for no good reason as soon as the car starts and, annoyingly, carries on for a good 5 minutes after it's turned off. I've looked online but have gone down a rabbit hole of coolant temp sensor replacements and all sorts and now I'm lost! Any advice welcome (with instructions please!). It's for my missus' RCZ which is a petrol 200. Cheers!

 

[Kerr]

Have you got a fault code reader?

No fault codes are showing up?

 

[2retro]

Yeah, only something about Headlight Washer Circuit Fault. Tried clearing it but the fan still going crazy...

 

[Verminator]

Wasn't this down to a relay

 

[2retro]

Wasn't this down to a relay

Any idea where its located?

 

[Pedro]

Check normal temp function of gauge as if it reaches correct temp with no deviations & does not rise & fall during warming up
Check Heater functionality full heat & lowest cold set
Check Air con functionality same as heating
The fan coming on from a cold start up is due to a command from the ECU a coolant fault has been detected this could mean temp sensor - thermostat- a fan relay & even a fault with the water pump as its electronically assisted the thermostat on my 200 was faulty & disabled my air con even though the engine temp was normal ?
I had the gas tested & was full so I changed the thermostat & cured that problem but never rule out a faulty fan relay as they can easily cause this issue

 

[2retro]

Thanks. Got some stuff to check then!

 

[2retro]

Update to this. Car also started missing, sounded like a lawn mower and drove like Reliant Robin. Replaced all 4 Coil Packs (of course! ) and now everything is suddenly cured! Still a fault showing with the 'Headlight Washer Circuit' but I'll figure that out at some point. Car runs perfectly again now and the fan has ceased trying to behave like it's trying to take off so all is good!

 

[2retro]

Engine light has gone away on its own as well today (7 trip logic must have cleared it) so WooHoo!