Thread: electric fan

naaa not really other than just getting a lil power boost to your engine (i read about 10% somewhere) and that the electric fans can cool your engine more efficiently at low rev, ie traffic jams but the viscous is better at high revs, mortorway and low range.
Oh and you can install a switch for water crossings but as yours is diesel it wont mak much odds either way.

the big advantage is that when you are zapping along at lots of KPH the natural airflow is usually enough to cool the engine so load is removed from the motor. however when running the electric fan draws its energy from the alternator so the same load is put on the engine.

The big problem comes when your slogging it slow the fans are working flat out (as is your aircon, fridge, lights and whole electrical load) you can wind up drawing the batteries down if the alternator doesnt have the headroom for the additional load (like say a series with a 35A alternator)

If your electric fan fails (cause you immersed it during a ford or something similar) your pooched if you dont have a spare mechanical fan. if a viscus fails to lock up you can rope it to the pully shaft to get you moving again.

I have seen many people write that they get a power gain by using an electric fan. I say that this might be correct if you compare it to a fan that is run on the fan belt all the time. The power gain/economy will come at highway speed where the natural airflow is enough to keep your cooling system cool enough.

With a viscous fan the fan only engages when the temp in the radiator is high enough that it causes magic to happen in the viscous hub with silicone oil etc and the fan engages, once cool enough the fan will disengage and you have the same savings as is claimed by the electric fan brigade.

The one thing that people don't often mention is that of efficiency. Remember you don't get something for nothing in the energy conservation game. The electric fan has to get its power from the alternator so you have now introduced two extra changes of energy exchange and each has an efficiency factor which will steal power. From the mechanical rotation of the crank shaft to the alternator into electrical form and then back to mechanical rotation on the electric fans again. I don't care how effecient your alternator and electric motor are, I'd say that the fan belt driving your viscous fan will have less losses than one belt and an electrical system.

Originally Posted by jx2mad

Does fitting an electric fan and removing the viscus blades serve any purpose other than removing some load off the motor. This is on a 110 def.diesel. Jim

I have both fitted to mine as i was trying to make my aircon more efficient at crawling pace(bit warm out here in the desert) but can't say it really made any difference to the aircon but the engine never ever gets hot

I ran my Tdi without the fan for a test and I buzzed the engine more times in that half hr than all time I've owned it combined.The engine revved it's head off in first like you wouldn't believe and I think running the ford twin fan set-up that overheating would not be an issue.The only trouble with the Tdi is the intercooler pipes are in the way so the fans won't fit.Running electric fans would be like having an extra cylinder,the fans are no more likely to fail than any other part of your vehicle if set up correctly and would make the hub bearing,a very costly fix last longer. Pat

Hi,lots of controlled tests have been done on Electric Fans compared to Viscus fans.The hp that a Viscus fan uses is far greater than even 2 electric fans when running.One point is that the twin electric fans cool the water down much quicker that a single viscus fan,so the electric fans would stop using engery much sooner than the single viscus fan.Also another point made is you are going to not have the posibale cracking of the timing case cover where the bearing for the Viscus fan sharft is.
Yes an electric fan can fail at any time,but the chances of both electric fans failing at the same time is not that great.(depends if they have been fitted corectly)
Electric fans do not use much power when running,put an ohms meter on them and see.
Another postive for electric fans is you have heaps of space between the front of the motor and the rad,makes working on the pulles/belts rely easy.
You dont need the plastic crowl behind the rad.
And you can keep your viscus fan in the tool box just in case the electrics fail,only takes 60 seconds to spin it onto the water spindel sharft.
The modern Defenders,TD5 and up,have so much electric junk fitted to them ,that electric fans failing is the least of you problems,
Well that just my view point,

I have a temperature switch on the cylinder head of my Defender 300 Tdi. The wire to the fuel solenoid goes through it. If head temperature gets to 105 degrees it opens and motor stops (at a much lower temperature than would do damage).

I changed the timing belt in May 2007. Since then the viscous fan has been stored behind the seats (in cab with 8 inch extension) in case it has been needed, which it hasn't yet. Do not have any electric fans installed either. There was formerly a small one in front of the air conditioner condensor. It seems to me that electic fans when switched off are significant wind obstructors so in marginal situations when in place, they have to be used. When not switched on, more air would go through the radiator without them if the vehicle is moving.

I have also removed / modified other things that obstruct wind ,including the shroud. It seems to me that the setup of it on Defenders with 300Tdi, especially behind the intercooler is an aerodynamic abomination. Have not had any heavy loads on the motor at low speeds and the switch has only opened and stopped the motor once in over two years. This occurred after idling for maybe half an hour in warm weather when the whole time I was expecting to be driving off within the next minute or two. If you are aware of this possiblity, it can usually be avoided. Maybe not with mechanical illiterates driving the vehicle though.

Note diesel engines are more efficient than petrol and for the same power output, less heat goes through the radiator and exhaust. A fan is only needed to force air through the radiator when heat is otherwise not dissipated fast enough.

Of interest is that in the 50's, an uncle of mine had a Riley sports car. One belt drove the generator and water pump and the other the fan. He drove it for eight years, largely around Melbourne with no fan belt. Including on very hot days past other cars with their bonnets up. Especially FJ Holdens, supposedly designed for Australian conditions! The only time overheating was potential problem was with prolonged idling at lights.

Replacing my air conditioner condensor is a low priority but probably will have to think about some sort of fan setup with it. Like the idea of two side by side fans driven via belt and electromagnetic clutch but would first need to move water and air hoses behind the intercooler.

The replacement condensor I have will go in front of the radiator only, NOT the intercooler. The more it can cool air, the better. It has coarser fins than standard so efficiency would be reduced when clean. Importantly though, it would not block up as quickly as a standard one and be easier to clean. Also connected with flexible hoses so it can be leaned forward to make blowing dirt out of the radiator easier.

When you reduce limitations on radiator efficiency, in many combinations of circumstances the need for a fan is greatly reduced.

Originally Posted by defend

Hi,lots of controlled tests have been done on Electric Fans compared to Viscus fans.The hp that a Viscus fan uses is far greater than even 2 electric fans when running. .....

Do we have any copies of the results of these controlled tests?

Originally Posted by defend

.......One point is that the twin electric fans cool the water down much quicker that a single viscus fan,so the electric fans would stop using engery much sooner than the single viscus fan..........

.....Electric fans do not use much power when running,put an ohms meter on them and see.

I suspect that the viscous fan will run for a shorter period than the electric fans. But then that is just my opinion.

Originally Posted by PAT303

.........Running electric fans would be like having an extra cylinder........

Yes I can believe that if it happens that the fan cuts in when you need every last bit of power as you'are climbing up a hill wanting to overtake some other car. But that is only possible because the fans can draw current from the battery and have the alternator charge it back later when the peak power demand is gone.