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Electric Fan Postion


Gnasha
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I fitted an electric fan some time ago and have had no problems so far. 

 

However, the fan is fitted on the front of the radiator and draws air through the radiator away from the engine is this correct?

 

When the car is in motion do you think the fan would be rotating by virtue of the air passing over the blades? if this is the case the fan would be rotating in the opposite direction to when it is electrically driven.  Would there be a likelyhood that the fan may cut in during this scenario?

 

comments would be much appreciated.

 

 

 

 

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The fan is incorrect. 

Check it is rotation the correct direction, fans are either suck/pull (for behind the rad) or blow/push for in front. And the blades only work well in one direction. Probably twice as well as when spinning the wrong way. 

Some fans are sold as universal, but then the blades have to be physically reversed.

 

Check which way the fan should be rotating, it may just be incorrectly wired need the wires reversed. Otherwise can the blade be reversed and swap the wires? Or fit behind the rad (though some fans have clearance issues depending on model.

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many thanks for the prompt feed back.

 

Its something that has bothered me for a while and just never got round to putting it into print.

 

I agree the best method would be to resposition the fan or turn the fan around rather that swop the wires.

 

Thanks again guys, enjoy the rest of you BH w/e

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Driving at night after fitting an electric fan with a dash switch that has an LED in the tip that glows when it's on, I noticed that it glowed when it was off!

Not brightly and the faster the brighter - the fan rotates in the air flow (mine is behind the rad - a test for a clean rad matrix) and acts as a generator!

 

John

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Yes, fans will free-wheel when they're not powered (acting as a generator), and this *probably* won't damage the fan - even if it's in the wrong direction. This is why a fan in front of the radiator, provided it's properly mounted, will be (almost) as effective as one behind. Any so called "masking" by the blades is virtually zero as they turn in the breeze. I'm rather interested in your "front + sucking" layout. (Were you on the CT forum several months ago?)

 

As has been said, blades need to be turning in the correct direction to get good efficiency, as they're an aerofoil profile - planes don't fly well backwards! However, unless there's something wrong with your cooling system, I think the fans will almost never come on while moving - mine don't.

 

So here's a wacky thought - if you could automatically sense the car was moving, run the fans inefficiently in reverse, blowing into the engine bay. When stationary run the fan in the correct direction, sucking the hot air out through the front!

 

I ran a thermocouple at the back of the engine bay on my Spit in hot weather last year and watched the temperature during normal driving. It was mostly down around 40- to 45'C, but pushed up after enthusiastic application of the loud pedal and would creep down after. However, sitting stationary in traffic (we get lots of that round here) would send the temperature soaring up to 60'C-plus. My twin XJ6/XJ40 pusher (air-con) fans (no mechanical fan) come on for 20- to 30-seconds every 4- or 5-minutes and bring the temp down by 5- or 10'C. What I really need to design is a "slow mode" for the fans so they waft air through in response to high temperatures in the engine bay - or fit a mechanical fan!

 

Cheers, Richard

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Richard I think you're on to something there.

 

This is wind activated.

 

http://www.ebay.co.uk/itm/GARDEN-OWL-DECOY-BIRD-SCARER-WIND-ACTIVATED-SPINNING-HEAD-SENSOR-HOOT-SOUND-/152090511578?hash=item23694d08da:g:bQQAAOSwInxXNayu

 

Mount it on your bonnet, hook it up to a raspberry Pi and some relays and you've done it.

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you dont need an wind activated  owl to scare the cats away,  there are other natural methods

 

keeps the wife out of the garden too !!!

 

Im an avid liker of engine driven fans on our cars ,keeps air flowing  under the bonnet  when stationary,

and load reduces as  the air rams through it over 30mph

  thinks its how our cars cooling was designed to operate.

 

  Pete

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But, Pete, you will have noted the use, by Triumph and other makers, of the 'viscous fan' that attempts to moderate fan action in response to engine temperature, and then that almost all moderns have electric fans, that do the same job, but better.   Old technology may have been fine at the time, but not today.  

John

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i agree John my 2000 has a viscous fan,   it turns at low speed and supposedly ramps down at higher revs 

what everyone gets into trouble with is high  underbonnet temperature variations  that our old design of fueling wont accomodate

keeping a steady flow when static is  pretty much essential if you dont want it all wooley  and stalled when its cooking in slow traffic.

 

and what ever fan drive you use in the end of the day the energy all comes from the fuel tank, be it mechanical or electrical.

 

as for moderns most engines face the wrong way so remote elec is the best option. apart from Issigonis cars

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Pete's correct it all come out of the petrol tank. A little known fact is the electric fan uses more energy, when in use, than a mechanical fan. This is because the process converts mechanical energy into electrical energy, generator, then back again to mechanical energy, electric fan. The mechanical fan run straight from the engines energy.  

 

The main advantage with electric fan is it only comes on when require. Shorter warm up time, No over cooling in the winter. Better cooling when stuck in traffic.

 

Disadvantages - if you drive your car hard in the summer chances are the electric fan will kick in and use more power than a mechanical type. When the electric fan stops working you could have over heating problems in the summer.

 

Dave 

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Possibly because the mechanical fan cools the whole engine bay, and there is likely some flow through the rad?

(sort of an aside) I have had heralds where in winter I have needed to blank 2/3rds of the rad to get he temp up to normal running temps. If the thermostat was working as we may expect, this wouldn't be necessary. And yes, thermostat tested etc, and this is on more than one car (probably 3 or 4!) Vitesse and GT6 never needed the rad blanking. No surprise there.

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this is one of those topics that can dive in all directions ....for ever  ha !

 

not been mentioned but cooling air over a tin rocker cover makes the  condensation mayo  ( brylcreme)  in the cover 

old winter  tricks were  

remove fan  !!  see   

fit baffle in front of rocker cover

lag the cover 

fit alloy or cast cover 

 

Pete

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Hello All

             While we are on the subject of fans I have 2 x 9" ones fitted to a full width radiator for 3 to 4years

 

While I was tinkering with my EFI and trying to get a steady tick over(another story!) the one fan cut in.

 

They are controlled by a dual thermostat and the right hand one (looking from front) comes on first and blows air across the alternator at 82deg the second is 88deg

 

I was thinking(dangerous!) would it be better for the left hand one to come one first and blow air over the throttle bodies and exhaust?

 

I do not suppose it would make much difference but every little helps?

 

The second fan never comes on only when I use the over ride switch(the one fan has coped in Spain and Italy in upper 30,s degs)

 

Roger

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post-44-0-98227000-1496256029_thumb.jpg

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I have one of the Aerofan variable-pitch fans where the blades turn against springs, so that the faster they turn the blades 'feather' so as to allow a good airflow but to reduce resistance. I've never fitted it to anything but I like the idea behind it.

 

 

post-151-0-88479100-1496257705_thumb.png

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I have one of the Aerofan variable-pitch fans where the blades turn against springs, so that the faster they turn the blades 'feather' so as to allow a good airflow but to reduce resistance. I've never fitted it to anything but I like the idea behind it.

I bet it would vibrate if all the springs are not very equal as they would all be at a different pitch?

 

roger

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 Hello All

             I have decided to change the fan control around(2 plugs to swap!)

 

I have carried out a scientific experiment on the change!(a thin strip of news paper hung a various places) and the air blows it against the bulkhead!

 

So it must be blowing between the side valences and the exhaust heat shield and engine so should help take a bit of heat from the exhaust when stationary?

 

Well that's the theory plus the one fan has been working for 3 to 4 years so time to use the other one as main one.

 

Plus it blows over the air box and IAT so may stop heat soak in this area?

 

Roger

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