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Wiring Fan To An Internall Switch.......

Has anyone done this on there Clio? I just want to be able to switch on the main cooling fan whenever I want, had it on my GTT but it was on the car when I bought it so has anyone done it and if yes how do you do it?

Cheers Marcus
  BMW 320d Sport

Never tried it but I assume youd just wire in either a 12v supply or an earth through a switch to the connection on the fan. Then whenever you want it you either put 12v on it or ground it, whichever way round it works, and then your fan goes on. Just a sinle pole/single throw switch will do. Get one from Maplins look for the letters SPST, a toggle style switch will be ok. Dont know how much current the fan draws though. Get a 15A toggle just to be on the safe side.
  Clio 1.6 16V

As Nick suggests, use a single pole switch and connect it in parallel across the the fan temperature sensor, which is normally isolated from earth and has two wires (ie. a wire from each of the two connections on the switch to each wire on the temperature sensor wires - normally the temp sensor switches the fan load down to earth). You can use a scotchbloc or preferrably solder/tape your connections at the sender and use spades at the switch on your dash.

I am a complete novice when it comes to all this!! But desperate to learn! Has anyone got time to do me a dummies guide? I see what the flying scotsman means just trying to put into relation to the wires that I am likely to find on the fan!

Cheers Marcus

Cheers for that mate I will have a look into it in the next few days.

Now just to figure, where to put the switch and how to wire it through from the engine bay!!

Cheers Again Marcus
  BMW 320d Sport

Are we assuming little electrical knowledge here? If so, here goes, everyones gotta start somewhere. Apologies in advance if its over simplified!

The circuit diagram above is correct. Youve got a 12v supply which ultimately comes from the battery + terminal, but which may actually go through other circuits beforehand. This is connected to one side of the motor via a fuse. If for any reason the fan motor circuit tries to draw more electrical current than is safe (which would cause a wiring or motor burn out), the fuse will blow and break the connection.

OK, so this fused 12v supply is going to one terminal on the motor, there will be another terminal on the motor which needs to be earthed to make the motor actually work; only when both the terminals are connected will the electrical current flow *through* the motor.

You can see an earth connection at the bottom of the diagram - this is simply a good connection to the metal chassis of the car which ultimately leads back to the - terminal of the battery.

The original circuit has only one switch in it, the temperature switch. Normally the switch is open (OFF) so the motor isnt earthed, and hence isnt working. When the temperature gets hot enough, the switch will close (turn ON) and then there is a clear path from the 12v supply on one side of the motor, through to the Earth connection on the other side, hence the motor starts up. Once the temperature gets low enough again, the switch opens and the motor turns off. Even though its a pretty simple system, it still amazes me how perfect the whole setup is.

Anyway, you can probably see that if you could somehow connect the motor to earth with another wire, between the motor and the temperature switch, the motor would be earthed and would turn on, regardless of the position of the switch. But youd need to get in the engine bay and touch the wire to earth every time you wanted to switch on the fan! If you could attach a wire permanently to ground, then feed it through into the dash, and also attach a wire permanently in between the motor and the temp switch, and feed that through to the dash, youd be half way there. Whenever you wanted the fan motor on, youd just twist the two wires together to connect them, and undo them to turn the motor off.

Then you could go one better and attach the ends of the two dashboard wires to a switch of your own, a toggle switch or a rocker switch, it doesnt really matter. Then when you switch it one way the circuit would connect and when you switch it the other way the circuit disconnects. On and off in other words. In the dash switch off position, the fan will still work perfectly normally, controlled by the temp switch under the bonnet. In the dash switch on position the fan will remain on, whether the temp switch is on or off.

Thats probably far too long or simplified really, but maybe itll be useful to any real electrical novices out there...and you did ask for a dummies guide!

What youre basically looking for is the fan motor. There will be two wires attached to it, a 12v and an earth. If one is red and one is black youre in luck. Red is always 12v and black is earth. One of them (probably the earth but it can be the 12v) will lead to the temp switch, and another wire will come out of that and on to ground, maybe a screw or something screwed into the metal of the car somewhere. Get a Scotchlock and crimp it (and another wire rated at 25A if thats what you think it needs) onto that wire between the motor and the temp switch. Pull your newly connected 25A wire across the engine bay, through the bulkhead, into the back of the dash and out to wherever you want it to be. crimp on a female spade connector and plug it onto the back of your 15A toggle switch. Take another length of the same 25A wire, crimp a female spade onto it and plug that in to the back of the switch, on the other terminal. It doesnt matter which way round they go. Take the other end of that wire and crimp a ring terminal on the end of it. Find an earthing point under the dash and attach it to that. An earthing point will usually have other ring terminals attached to it and will be a screw going into bare metal. Then try it out, find out which way is on and which way is off, and bobs your uncle.
  BMW 320d Sport

Well Im glad it helped! Just lmk if you look under the bonnet and its not obvious, dont cut or scotchlok anything until youre sure. Oh and btw disconnect the battery to be on the safe side. Just take the earth cable off, the positive can stay on.

If youre thinking about getting into electrics, a multimeter is essential really but you can get by with one of those little screwdrivers that light up when you touch a 12v supply. They only cost a few quid and that way you can be sure which wires are which. Whichever wire on the motor lights up is the one you *dont* want to chop into. Then just to be sure before you start routing wires through the bulkhead, try earthing the motor through your new scotchlocked wire just to see if it works. Remember to connect up your battery briefly just to test this.