Fan Switch

[Corolla52]

Hi

I was hoping someone could help me with this.
I want to wire my fan up so the ECU turns it on,
but I also have a on/off/on switch so i can override it.
All I have been told is that the ECU is supposed to switch
ground to the relay when it reaches the temp switch on
point. I have the ECU thena 4 pin relay [The relay is marked
30-power in, 85-earth 86 switch 87-power out] then a fuse
then the switch then the fan.

Thanks.

Stefan

[The Shrew]

On your temp switch you will have two wires. If you touch them together the fan should run. So If you attach a switch either side the temp sender you could switch the fan on and off this will work .

But

You want both the switch and temp sender to work this is the bit im unsure on. If you had the temp sender and switch attached, the switch was in the off position i will take a gues that the fan will work as normal but you could also switch the fan on before the fan would normally kick in if you wanted.

Im not very good at electrics so hopefully someone could clarify / correct what i have suggested.

[Belatti]

I was thinking about this, too. However I use Fuel Tech.

I am thinking in discontecting the alternator when the car is on full throttle, too. I have found that teams without alternator in their cars have reliability problems.

[phoenix]

Originally Posted by Corolla52

Hi

I was hoping someone could help me with this.
I want to wire my fan up so the ECU turns it on,
but I also have a on/off/on switch so i can override it.
All I have been told is that the ECU is supposed to switch
ground to the relay when it reaches the temp switch on
point. I have the ECU thena 4 pin relay [The relay is marked
30-power in, 85-earth 86 switch 87-power out] then a fuse
then the switch then the fan.

Thanks.

Stefan

Here is one way to turn the fan on and off via the ECU:

Connect pin 30 of the relay to a suitably fused power supply from the battery or from the switched side of the master cutout switch if you have/are required to have one fitted. Fuse rating and wire gauge will depend on the current rating of your cooling fan.

Connect pin 86 of the relay to pin 30 of the relay. Or, if you want the fan to turn off when you turn off the ignition, connect pin 86 of the relay to a 12 volt supply that is only live when the ignition switch is 'on'.

Connect pin 87 of the relay to the +ve side of your cooling fan. Again use a gauge of wire that is suitable for the current the fan will draw. The other wire from the cooling fan (there should be only one if it is a single speed fan) should be connected to earth/the chassis.

Connect pin 85 of your relay to the fan pin on the ECU that is the 'output' for the cooling fan.

[Corolla52]

Thanks for that Phoenix.

Stefan