Thread: Electric cooling fans

My Stage 1's fan shattered - replacement would have cost about the same as the electric setup I put in. I bought 2 12 inch electric fans, a controller unit and a sheet of marine ply. The 2 fans were because there wasn't enough clearance in front of the viscous drive shaft to put one fan in front. Used a short length of old aluminium pole, cut to size and along the length, to replace the fan on the driveshaft.

In an ideal world would have a 15 inch on one side where there's a little more clearance.

Fuels savings? No idea - didn't have the car long enough before I did the conversion to tell. On the highway the fan doesn't run at all, so there must be some. I'll go take some photos and post them.

My reasoning with the ply backing was (1) something to mount the fan to and (2) allows the fans to draw across the whole radiator. Not sure if that's necessary though.

Photo of the Stage 1 setup:



The long bolts are because that's what I had lying around. Down the bottom there's a second strip of ply which runs across the bottom and is loosely rivetted to the main sheet - this sits in the channel at the bottom of the radiator. The whole assembly is held on with screws as per the original guard.

Running a tape measure, the fans are a little under 12 inches. There's room for a larger one on the left of the vehicle (bottom of the photo)

I have mucked around with electric fans on my Rangie for years. The last set were a set of EF falcon fans. I can honestly say they make absolutely no difference to the fuel economy, the temp fluctutes more if you dont want them cycling on and off very quickly and they use heaps of power. Somewhere between 30-40 amps. I blew a 30 amp fuse but the 40 was ok. Using all that power constantly puts a noticable drag on the alternator (and the motor) and the alternator belt needed continually replacing every 4-6 months. The only advantage I can see is that the fans can be switched off for river crossings. I am sure others will have a different opinion.

Ian

Hi guys, does anyone else in here not know the purpose and/or function of the 'viscous' bit of 'viscous fan'? Is it like a fluid coupling on a big gear unit, i.e. reduces the wallop on start up?

Disco '96 V8i (vrmm, burble)

The primary purpose of the viscous coupling is to allow the fan to rotate at the pulley speed when idling, but as the rpm increases and the turning resistance of the fan increases as it tries to move more air, it does not speed up as much as the pulley does. The fixed fan fitted to most earlier engines moves far more air than needed at high rpm if it is designed to move enough air at idling and low rpm.
An alternative to the viscous coupling is used on, for example, the Isuzu engine on my 110 - it has a nylon fan designed so that the fan blades bend under increasing load so as to decrease their angle of attack for a similar effect.
The advantage of an electric fan is that it can be switched off when not needed, which for most cars, is most of the time.
All of these gadgets are to save a little fuel and keep the engine quieter.
John

Thanks JD. My reason for the electric fan was I could build one myself in the afternoon, while I was told that a replacement for the viscous-coupled fan would have to be shipped from the UK (!!) Anything else was a bonus.

Now, if I'd known about AULRO I might have found that elusive fan and saved myself the trouble...

Steve

Neither markyc or JDNSW mentioned the thermatic feature of most viscous fans.

The non-technical description is a valve in the viscous hub, which opens/closes at preset temps. The valve controls the flow of viscous fluid in the coupling.

The result is that the hub can transfer more torque to the fan blades (for more air flow) when the temp increases to the set point. And less torque when the temps are lower to reduce power/noise.

Yes, I was aware of the thermatic feature, but keeping it simple.

One comment I would add on electric fans - my son recently cooked the motor in his Kia Rio - turns out the reason this happened was that the brushes wore out on the fan motor ($5 fix - but not the motor, it was around $1000). So if you rely on an electric fan, remember that they don't always last forever.
John