As per the title, recently my radiator fans are both on constantly, even when the engine is cold.
The fans do switch off when the ignition is off, but if you turn it on, without starting the car, both fans switch on at full whack.

I've swapped both relays from another S (cooling fan and AC cooling fan) and this didn't resolve the issue, so I don't think it's relays.
I've tried reaching down to ensure the fan switch is connected correctly, and it all feels ok.

Engine temps are otherwise all fine, and show as expected on the dash.

I've tried following the wires from the fanswitch in the rad, and it goes up into the loom attached to the wing. From there, there is an earth with a bunch of wires attached. Is it worth taking this off and giving it a clean?

Could it be the fan switch that's gone, or the thermostat? If it is the switch, would the mishomoto one (£25) fit, or would the Mugen one be a better replacement? Both seem to have a lower switch on rate. I presume the cooling system needs to be drained to replace this? https://www.s2ki.com/s2000/topic/107...9#entry1392289 ?

Any other ideas?

I've recently had to put in a new Yuasa battery as the other one wouldn't take a full charge (or at least, the 'eye' never went green) so don't want the new battery getting extra drain.

Cheers

 

Mine was recently doing the same because a dodgy fan switch. i diagnosed mine by unplugging it. The fans then stayed off when putting the ignition was on. Told me that the switch was activating below the temperature threshold.

Fitting a new one did however mean draining the coolant. If you do it be really carful to bleed the system completely of air when refilling.

 

Mine did the same and i just changed the radiator switch, I didn't drain the coolant, I just swapped it over quickly without loosing too much coolant.

 

Since you're draining the engine coolant replace it with new Honda coolant since it's probably been 3 or more years since you changed yours.

Two gallons should do it.

-- Chuck

 

Cheers for the responses guys. What switch did you replace with? OEM or aftermarket?

 

I replaced mine with an aftermarket one. 3 years down the line and no drama Cambiare was the brand.

 

I found aftermarket cheaper than oem from Si at Hendy