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MG Midget and Sprite Technical - Cheap electric cooling fan

Hi
I know Kenlowe and Revotec are the electric fans of choice by many. But they are quite expensive
Has anyone had experience with some of the cheaper ones available. For example, I've seen some on ebay for only £15. Is the problem with the cheaper ones that less air is moved, less reliability, or is it just much less money for a similar result?
Be interested if someone has had experience with both - thanks
Graham V

I used a scrapyard one. Ex Rover 400. £5 complete with a cowling that neatly fits in front of the rad.
GuyW

I did the same as Guy except that mine is from some Japanese car, I don't remember which one. Cheap and reliable. All I had to do was make some brackets and wire it.
Martin

Think mine came off an old Metro, easy fit to the front of the rad cowling.
SR Smith 1

Hi Graham same as Martin, SR and Guy, Toyota 12 inch
Fitted in front of the rad with a modified cowling to inprove airflow (see pic) thermoswitch fitted to the top rad tank with a relay and an overide switch
Works fine
Cheers
Rod

R W Bowers

Sounds like an excellent idea, guys. I've got a 1500 that works well down here when it's really hot except when I'm sitting in traffic!
How did you wire it in? With a thermostat (which one) or just with a manual dash switch and did you need a relay.
Tony Wood

I'm off to the scrappers today to pick one up. Ditch the engine driven one.
Karl Bielby

Hi Tony
185 F should be Ok, fitted to the top radiator tank
Standard 30/40 amp fused relay (see pic) can be mounted anywhere convenient, mine's on the firewall behind the wiper motor. Wired directly to the battery means that the fan may run on after you switch off, if you don't like this wire it through the ignition.
Overide switch on the dash, Indicator light on when the fan is on.
HTH
Cheers
Rod

R W Bowers

Electric, - and remove the mechanical one - is definitely the way to go. The problem with the mechanical one is that it runs continuously irrespective of the need. It saps power (about 4hp I believe) and adds to the general noise under the bonnet.
My electric is controlled by a thermostatic switch in the top hose, with a manual override switch and indicating light on the dash, and fused relay.

In practice, the fan only very rarely comes on. Forward motion of the car at anything above about 20mph is sufficient on its own to drive air through the radiator core and maintain proper running temperature. So the fan only switches on in very heavy stop start traffic, which I rarely encounter.

The only confusing thing is that above about 65mph the fan indicator light begins to come on as the fan motor begins to act as a dynamo, presumably then putting out more than 12v and reversing the flow through the bulb.
GuyW

Fitted a Revotec one (cheap on ebay) from a classic Mini,
~ thermostat control,
~ relay (mounted on n/s inner wing just forward of the carbs (on an A series) (see photo - bottom rh corner of engine bay, red connector shows the relay body)
~ plus manual override switch - just in case.
No worrying on hot days stuck in traffic :)

J Tickle

Guy

For it to reverse the flow through the bulb, you would need a permanent live to the bulb and switched ground.

More likely that you are switching live to the fan and bulb, then when the fan turns due to forward motion, it is generating a small voltage causing the bulb to glow.

If you switch via a relay and wire the bulb in parallel with the relay, the fan spinning won't light the bulb.
Dave O'Neill 2

Thanks Dave,
I need to think my way through this! AFAIR I wired the dash switch to activate the relay, as does the thermostatic switch. I think I then wired the bulb in with the fan as I wanted it to show me when the fan was working, not just when I operated the switch as I can easily see when that is in the on position!
GuyW

Yes, that makes sense.

I think the only way round it would be to either use a second relay to light the bulb, or a diode in the feed to the fan to stop the reverse flow.

I suppose the other option would be to use the relay to switch the fan and bulb to ground. They would each need a live supply.
Dave O'Neill 2

The fitting of the thermostat is the only thing that I'm not sure about. An electric one fitted to the top nearside of the 1500 rad would be ideal, but I've got a new rad and don't fancy butchering it just yet!
The alternative is the variable stat box with the sensor slipped under the top hose - the advantage with these is that they are adjustable.
Has anyone had experience with them and which would be the one to go for?
Tony Wood

Just a thought, Guy, you said you used a Rover 200/400 fan in front of the rad. Looking at some of the photos on ebay they look as though they are designed as "pullers" not "pushers". So did you just reverse the electrics to turn it into a pusher?
Tony Wood

I cannot remember how I did it - It is mounted in the air duct in front of the rad, and definitely "pushes" the air towards the rear, through the rad core. Maybe I reversed the polarity - I would have just connected it up and checked to see which way the fan blades rotated. As the whole thing is plastic I guess it could be wired either way round.

For the thermostat switch I used an in-line MDPE housing that splices into the top hose with a couple of jubilee clips. Burton Power used to sell them but that particular one is now listed as NLA.
GuyW

Photo of the fan as installed. It spins clockwise as viewed. Someone will tell me its wrong, but it works! ;-)

PS, I better add that the wiring has been tidied up a bit since then !

GuyW

Guy,

ditto here. Originally a puller mine's set up to push (by spinning backwards) and it works probably not as efficiently as designed but heh it keeps the engine cooler than the always on mechanical fan and probably liberates all of a horsepower! Win win LOL.
J Tickle

Guy, you'll be pleased to know that your fan is fitted the correct way. 😀

It is fitted in the same orientation that it would have been, originally.

The side of the fan that is visible would have been against the inside of the rad. If you had fitted that side against the outside of your rad, you would have needed to reverse the polarity to achieve air flow in the correct direction, however it wouldn't have worked efficiently due to the shape of the blades.
Dave O'Neill 2

Thanks for the positive vote Dave! I only really posted it because folk like photos from time to time.

I am no expert in fluid dynamics, but I thought of it this way: When it rotates clockwise the curved blades look like they would sort of scoop the air way from you and give it a kick towards the centre. And each blade also has a sort of aerofoil cross section which would create increased pressure on the rear concave surface, and a corresponding low pressure on the convex front surface, sucking the air in towards the spinning blade.
GuyW

Correct rotation and operation also seems to be confirmed by the arrow which is visible on the hub when the image is zoomed in that area.
David Billington

exactly the same as my Rover 200 fan. Runs the same way.

Mine's controlled from the Emerald ECU. But that's cheating. On at 105C of at 98C. Coupled with the standard 1275 radiator keeps 120bhp of K series cool in all weathers.
Rob Armstrong

to add, on the P6 I use 2 of these

http://www.ebay.co.uk/itm/14-14-Inch-Slim-Line-Universal-Electric-12v-Radiator-Intercooler-Cooling-Fan-/400542229248?hash=item5d422d6300:g:2HcAAOSwa-dWjOzK

as you can't get a big one in the middle as it hits the nose of the water pump. 1 on either side works great.
Rob Armstrong

Rob
would you say they work almost as well as the much more expensive ones?
Graham V

Hi Graham V
Refer to diagram for a simple wiring method.
An indicator light can be wired in parallel with the fan and will light when the thermo switch or the manual switch are on.
There is a way to use a 5 pin relay to short the fan motor to earth when not switched on to stop it freewheeling too badly, this generally will stop any indicator lights from glowing. This uses terminal 87A connected to earth and then connected via pin 30 to the motor +12v) when the relay is normally closed. When the relay is energised pin 30 is disconnected from the earth (pin 87A) and connected to the battery through pin 87 and the fan runs. This reverses pins 87 and 30 so be careful.
A bit complicated as you also have to mess with the switching.
As you can see the fan will not run unless the ignition is on.

HTH
Cheers
Rod

R W Bowers

I might try that Rod,
Presumably if pin 86 went to a permanent live instead of the ignition, then the fan would run on after switching the engine off, until the thermoswitch cut out. The danger is if you have used the over-ride then one might forget and leave that on and come back to a flat battery later!
GuyW

And without the water pump - you're only cooling the water in the rad not the block. Really doesn't seem worth it.

I have mine wired as per Rod's diag - with an LED light in parallel to the fan. I do get the light dimly lit (visible at night) when the fan is freewheeling at speed. I've never got round to acquiring a diode of sufficient rating to put in the fan side to stop it.
Dean Smith ('73 RWA)

Suppose so. Most modern cars seem to use run-on fans. But I guess alloy heads are more prone to damage from localised overheating as the hot water rises to the top
GuyW

I use one of these with a green led. It's permanently live and is bright enough for me to leave the car with the fan running.
http://www.carbuildersolutions.com/uk/led-illuminated-paddle-toggle-switch-green

J Tickle

Afraid I can't answer the question about the expensive ones, I've never tried an expensive one! All I can say is they work :)
Rob Armstrong

'and is bright enough for me to leave the car with the fan running.' should of course read 'not to leave the car...'
Apologies.Doh.
J Tickle

My e39 used to have an electric water pump as well than ran on after if it was too hot still!


What size fans are you guys running? I had a look today and the rad is minute!! Not a lot of space in front of it either!
Karl Bielby

Hi Guys
Modern cars are set and forget. A lot of the charm with classic cars is controlling things manually, give me a manual override any day.
Cheers all
Rod
R W Bowers

Ive got a cheap fan in the race car and its never let me down - mounted behind the rad and it gives a really good airflow.A bit like R W Bowers - I have a simple on-off switch. Have a Revotec sensor plumbed into the top hose but its not wired in - prefer to keep an eye on the temp and turn on the fan if idling too long rather than trust the electronics.
John Collinson

Must be a slim fan to fit behind? Or is the engine driven one quite thick?
Karl Bielby

Some years ago my fan relay failed and turned the fan on in the car park. I got back to the car and there wasn't even enough juice for a push start. Wired through ignition now.
L B Rose

This thread was discussed between 11/09/2016 and 23/09/2016

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