Just completed refreshing the cooling system including new hoses and upgraded radiator. The radiator had the otter switch replaced with Brass fan switch which activates at 82°C, deactivates at 72°C. M22 x 1.5 thread. The radiator filler is no longer on the radiator with the filler now replaced by the Coolermaster Thermostat housing which includes the filler.
However having connected it all up using the original wires of the old otter unit the fan doesn’t want to kick in. If you join the wires together the fan does work ok. Am I missing something???
If the fan goes when you join the wires to the switch then it looks like your switch is faulty
.. so take the fan switch off the radiator and test its operation with a kettle, a thermometer and a multimeter set on the"continuity" function..Tony
「いいね！」 2
Yes fan does run when wires connected, though the switch is a new one from Cooler Master. I’ll try taking the switch out and doing a hot water test with a meter…
Tony, will give it a shot but the switch is new from cooler master 
When you join the wires up to the switch, what is the temperature of the water in the radiator? If it’s 82 degrees or higher and still no fan then I agree with the others that the switch is faulty.
A good mod is to run a 2 core cable from the wires at the back of the radiator switch to a on/ off switch under or near the dash so you can manually switch the fan on if needed for summer traffic jams ?
I agree with Steve above, a secondary switch when in hot traffic is a good safety precayution. Fitted in mine with a tell tale light to show when in use, lest you forget
Tony
Here’s my heath robinson test rig using multimeter but still no joy, is this the correct process. Tried setting meter just to beep on complete circuit and my usual 12v test.
If your meter beeps when you put the probes together, but no beep across the thermoswitch contacts above the specified temperature, suggests the switch is indeed duff..Tony
「いいね！」 1
Been back to the fan switch supplier, it appears that you need to include a relay in your installation with the fan switch.
They actually have a very low current tolerance, so should be operated through a 4 pin 30 or 40 amp relay.
It does actually mention the relay on both the online and catalogue listings, but if you are in regular contact with the club with recommend one of these two items depending on if just a relay is required, or a full wiring kit…
https://www.carbuilder.com/products/black-standard-relay-30-amp-4-pin?variant=41978057556022
https://www.carbuilder.com/products/lighting-and-accessory-relay-wiring-kit?variant=41978228834358
Do they mean that the thermo switch was burnt out by the current drawn by the fan..?
Tony
Unrelated - but the little black pump next to the radiator appears to be the screen washer pump. Is that right? Would you report some details about it? Make, vendor, etc.
I’ve bought a couple of washer pumps from the usual suspects but they have been hopeless. They look nice and original but both failed in a few months.
Nick
Hi
82c seems very low for the fan to kick in. Does the engine not run more efficiently and gunk up less at higher temperatures? Also what is the point of a switch for summer driving? The fan will be running, so a switch is superfluous. The light to inform when the fan is operating is somewhat useful. I may well fit one to my car.
As an aside I run a Zetec +2, and I have a similar brass switch that comes on at 100c. The car runs between 90-100c in the normal way of things. The same engine in a Ford Focus activates the fan at 110c as standard.
Berni
Apparently, anyway will set up a rig with the 6ra relay and simulate using the hot water bath 
If the switch is working a multimeter and thermal bath will show it. If that’s the case then you can set up the needed relay when you install it in the car. If not you need a new switch
cheers
Rohan
First off with your set up does the meter beep when the two wires are put together - if so that is correct, if not then you need to set the meter up properly so it does.
Then connect up the thermostat switch and heat it up in the pan of water. If the water gets to 100 degrees (I.e. boiling) and the meter doesn’t beep then the switch is faulty.
For the test a relay is not needed as you are testing for continuity.
「いいね！」 1
The benefit of an overide switch is that you can switch on the fan early (to maintain a normal temperature) rather than sit staring at the gauge rise while you wait for the fan to kick-in. Temporary slow moving traffic, stuck at road works lights etc. Plus you have a means of testing the fan before you set off.
Mike
Could be 
but now all gone