todays question, wiring in the fan (rad)

[bill]

hi, once again, I would like to wire the fan to a switch on the dash, I would like it to run on when the ignition has been turned off, is this the correct way and any ideas on how to do it.

than you.

bill.

[ColinMarr]

Bill,

Controlling the fan via a panel switch is not a good idea – it takes lots of current and should be controlled by a thermostat via a relay. The thermostat switch should be on the bottom of the radiator (probably covered with grot) and the relay down near the air inlet pipe. An alternative position for the thermostat switch is on the water pump, but this is not as good as on the rad itself. Wherever it is located, when hot, the fan will run on – excessively so if its on the pump!

Do you have a circuit diagram?

Colin

[bill]

hi colin, I think I have a wiring diagram, I can see the thermostat on the bottom of the rad. with two wires going to it,  the fan has two short wires male and female spades cannot see where these could go no wires near.
apart from one red wire which looks like a spark plug cap I think that has a male spade and is live all the time. hope this makes sense.

cheers
bill.

[ncundy]

The fan has a permenant feed (from the stater motor terminal). If its not working then check the wiring, the function of the thermostat, the relay and the fuse. As Colin says, it should run on.

[ncundy]

Here is the fan circuit:

6 ) fan
7 ) thermostat
8 ) relay
14 ) fuse (in a small bullet holder)
15 ) starter motor

Edited because if I use number and single paranthesis (without a space between) I get all kinds of smilies 

[chugga boom]

usefull to know that a peugeot 205GTI fan switch fits and works exactly like the origional and are only abot 4quid! i usually just change them for a new one at that kind of money, even has the same connections, i think from memory there are 2 variants available for the pug a 2 wire and 3 wire type , just use the 2 wire type

[bill]

hi thanks for all the replies, I am not the brightest kid on the block when it comes to electrics I can see red thicker cable coming from the solenoid, that is live all the time would that go to the fan? will take the air filter off tomorrow and have a good look.

thank you once more.

bill.

[Neil Lewis]

A different way of wiring it.

It's true that the relay is controlled by the thermostat in the radiator but many people don't realise that it actually switches the earth side of the fan motor,  That means that there is always a live feed to the fan even with the ignition switched off.

I did away with the relay on my Fulvia 3 and connected the fan earth directly to the thermostat.  That's the way it works on most (if not all) modern cars and, being the earh side, there's no danger of sparks across the thermostat terminals.  It worked on my rally Fulvia for many years like that (maybe 80,000 miles).  The relay over-complicates the circuit and removing it means one fewer thing to go wrong.  And when you are relying on the fan cutting in to keep the engine from overheating, that's a big consideration.

Neil

[ColinMarr]

Neil,

I like the sound of that! But it does mean that the thermostat switch takes the full current, which I guess would be up to 20 amps. If it’s happy with that then fine, but I would have thought it would only expect to see a maximum of a few amps.

Colin

[lancialulu]

My 1.3 has thermostat on the pump and suspect if the fan runs on then some cooling through thermosyphoning will continue to cool the engine water.

My 1.6 Sport in the more normal and has a parrallel switch to the thermostat to manually override. It uses a standard fulvia illuminated dash pull switch so that when the fan comes on automatically it has the by product of letting you know its come on. On my sport it has so much sound deadening you cant hear the fan most times.

Tim

[bill]

hi once more, removed the air filter and found the blue wire tucked away, what threw me was the live wire direct to the fan, when I read Neils quote this morning that the switch was on the earth side the penny dropped, (sort of) so all wired up now, one bonus I found a switch that can bring the fan on from inside the car.

one final thing I just noticed  the oil I put into the car was semi synthetic (10/40) will this be ok or should change it?

 I would just like to thank everyone for the intrest shown in my questions

Bill.

[Neil Lewis]

Neil,

I like the sound of that! But it does mean that the thermostat switch takes the full current, which I guess would be up to 20 amps. If it’s happy with that then fine, but I would have thought it would only expect to see a maximum of a few amps.

Colin

Hi Colin

That's the whole point.  The fan is switched on the earth side so the current passing through is quite small.  It isn't switching 12 volts.  It worked reliably for me over many years with no problem and my car had to work quite hard with teh rallies it did.

Neil

[Philm]

I think the oil sounds a bit thin?

[lancialulu]

Agreed - I use 20-50 classic duckhams or 10-60 Castrol synth for 1600's

Tim