27-08-2018
From the past couple weeks, it had been noticed that the radiator and A/C radiator fans turn on immediately after pre ignition, engine start and on a cold engine. The engine temperature would be ok and no overheating was present.
The radiator fan should only switch on when the coolant reaches a certain temperature, I think around 93-95 degrees. I set about to find out what was wrong.
Thanks to a few old s2ki forum threads, I performed a few tests to find a root cause to the problem.
The threads pin pointed the radiator fan switch to be the most likely problem.
I performed a few tests to confirm this:
-Swapped over the radiator fan switch relay (there is an identical relay within the fuse box)
Result: No difference
-Disconnect the radiator fan switch itself
(fan switch is located on the left hand bottom section of the radiator)
Result: On pre-ignition, engine start and cold engine, the radiator fans do not switch on.
With the above findings it concluded that the existing radiator fan switch is stuck in the closed position.
I am all for sourcing and using genuine Honda parts but for something quite relatively easy to change, several members have recommended a good after market brand.
The Honda OEM part, cheapest I found was £67.00 (Usual RRP £94.00)
After market type: £13.04
The brand of the aftermarket type was Canbiare which is a well known European brand.
I decided to go for this one.

The switch was relatively easy to access, and from several threads it required no coolant bleeding when swapping it out within the radiator which was a plus point.
The lower under tray was a tad tricky to remove with most of its clips crumbling upon removal.
It would seem that it had never been removed.
With the under tray removed, a good general clean was also performed.
The radiator fan switch has a size 24mm hex and a deep socket was required to remove it.
I realised this quite late and didn't have one in the tool box.
A trip to Halfords solved this.
Just a little spillage of coolant during the quick swap over and that was it.
The radiator fan switch is located at the bottom of the radiator when the red arrow is pointing.

Upon engine start and warm-up the fans kicked in as normal and switched off as expected.
A long 40 min drive confirmed full function had been restored.
The old radiator fan switch removed

Parts Purchased:
Part: Radiator Fan Switch
Honda Part Number: 37760-P00003
Canbiare Part Number: VE709047
Supplier: Car Parts In Motion (Ebay Seller)
Tool: 24mm Deep 1/2 inch Socket
Supplier: Halfords
https://www.halfords.com/workshop-tools ... -1-2-drive
Services Used:
None
Resources used
S2ki Thread: Fans Always on
https://www.s2ki.com/forums/uk-ireland- ... s-1131621/
Thread I Started
https://www.s2ki.com/forums/uk-ireland- ... t-1187554/
Thanks to Wurlycorner for recommending the Cambiare brand
http://www.ludegeneration.co.uk/viewtop ... =5&t=22229