Cheap electric fan conversion using new parts.

[Alburglar]

I've had the car off the road for various different reasons and thought it was a good time to do an electric fan conversion and was surprised at how cheap it was!
universal 12" electric fan on ebay was £25 delivered.

fan switch was £15
http://www.cbsonline.co.uk/product/Fan_ ... 1.5_FANSW2
I am using it as an auxillary fan at the moment so i bought a swith that doesn't turn on till 100c and turns off at 95c. M14 x 1.5mm thread.

4 pin fused relay was a couple of quid I think.

[Minimayhem81]

Hello how did you screw the switch in to the radiator because on mine its just a plastic blank i would have to drill it out and then i would only be screwing in to plastic....not good lol

[Alburglar]

Mine had a blank in that looked like a bolt, I just used a spanner.

[Brianmoooore]

Strange mod. to do. There's no shortage of room for an engine driven viscous fan on a four pot, so what's the purpose of the change?
Non genuine replacement rads. usually have a blanking plug, as do all aircon rads., of course. The original rad., or, I think, a genuine replacement, will just have a raised ring in the plastic where the switch boss would be.

[Minimayhem81]

The change is mainly to save on engine power it takes more power to spin that fan, normally about 8bhp? and why do you need the fan going if your doing 70mph down the motorway? might as well save the fuel and not bother you only need the fan going when your in traffic.
Yes having an electric fan will take power because its making the alternator work harder but your always running the alternator anyway so might as well use it.
Anyway i better go have a closer look at my rad see if i was blind and its just a blanking bolt cheers!

[rix313]

normally about 8bhp?

You wont be seeing 8bhp from removing the viscous fan.

[craigieeb]

Mebbies 0.1 bhp

[Minimayhem81]

ok well it might not be as much as 8bhp but still the engine will rev more freely and have less losses...

[ed325i]

What would be a good temp for the fan to turn on?

Ed

[fuzzy]

always disconnect the battery when working on an electric fan....theres pics on here somewhere of the mess they made of my hand when it turned itself on

[Minimayhem81]

err like 90-95 degrees?

[Brianmoooore]

but your always running the alternator anyway so might as well use it.

Your knowledge of physics is slightly lacking!
As said above, a fan driven by a viscous coupling absorbs very little power when it isn't locked, and I'm afraid an alternator doesn't behave like you think.
If we assume that an electric fan motor has a power of around 0.3 hp, then it will consume about 0.4 hp of electricity to drive it. To produce this amount of extra electricity from the alternator, it will absorb just over half a hp from the engine. Alternators under load don't spin like they do in your hand. A fully loaded alternator will take a couple of hp to drive it!

[Minimayhem81]

i never said its as free when under load as if it were in your hand lol anyway yes it takes more hp to run the alternator because of the extra power required but unlike the fixed fan its not on all time its only on when you stop for a traffic light or a roundabout... whatever it is its not on for very long. Please tell me why out of all modern cars today, all have electric fans?

[Brianmoooore]

Most modern cars have electric fans because the radiator is alongside the engine instead of in front of it.
E30s don't have a fixed fan. They have a fan with a viscous coupling between the pump pulley and the fan, and the viscous coupling responds to the increase in coolant temperature when there is little airflow through the rad. in exactly the same way as an electrical thermoswitch fitted to the rad. does.
I.E. It switches the fan on, but with greater reliability and greater efficiency. As soon as the coolant temperature in the rad. is a few degrees below the normal engine running temperature, they both switch the fan off.

[Minimayhem81]

fair enough i didnt know that... though it was only a viscus fan ie just filled with oil, not one that responds to the fluid temps

[chu346]

Why didn't you wire through the fuse box?