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MG Midget and Sprite Technical - electric / belt fan

Is there real advantage for one of the two? I can image both having their pors en cons.

Curious what you think
a.o. arnold

Electric fans make the engine bay a lot quieter, and sap less engine power. They can also be set up to be most efficient at low speeds which is when they are needed most. At higher speeds there should be enough air movement forced through the radiator anyway.
GuyW

An electric fan gives you extra thrust on launch if you have a manual switch in the circuit!

You can let the electric fan run when the engine's not going if you need to cool things down, though I'm not sure how effective that really is because, when the engine's not running you're only cooling what's in the radiator as the coolant's not being pumped round - unless you've also got an electric pump that is.

The only real plus points are as Guy says: a quieter engine bay and less engine power lost in driving the fan and this might give an improvement in fuel consumption. There must be some additional electric load which the engine will have to absorb but only when the thermostat cuts in.

One final thought: With an electric fan you're also less likely to get hit or have dangly things caught by a whirling fan if you reach into the engine bay when the engine's running.
C Mee

Having run an electric only cooling fan, year round, for many years on my midget (and without override switch) here's what I've found.

The electric fan isn't running when it's not needed, when the engine is cold and at higher speeds. So the engine warms up quicker, particularly in winter, and there might be a tiny bit more power at higher speeds.

Unless you get your own thermoswitches the fan can stay on too long and/or to avoid cycling set to come on a bit higher than strictly wanted.

I don't think overall there is much of a power gain as the extra alternator "drag" on the engine could even things out.

The electric fan is quiet when it's not on but at low speeds it can be noisy. It is less steady in heat control if you don't have a good range on the thermoswitch.

I wired mine to remain on after the ignition was off and it got the heat soak temperature down but meant it was running off the battery (noisily) without much real gain unless the car was to be driven very shortly after.

I see little point in an override switch unless you're the nervous type, you don't have one in modern cars.

A fan engine side of the rad is better and more efficient, bumper side of the rad restricts a little airflow (and fan size) and is good for debris collection (surprisingly so).

Belt fan is absolutely fine, works well, not so good if you use a lot from cold and in colder weather because it slows down the warming of the engine and when it's not needed it's going fastest but when it's most needed it's going slowest - but it works fine.

Nigel Atkins

Electric fan c/w adjustable Otter/thermo switch every time. Engine driven fans are hugely wasteful. My old mk3 electric fan hardly ever cut in as air through the rad was sufficient to cool things down, even at slow speeds for a while. Flushing the system also makes life easier.

An electric fan can however energize at any moment - even when the ignition is off. In that sense it is more risky than an engine driven fan.
Oggers

Has anyone tried to fit a viscous coupled fan to a Spridget?
anamnesis

There was one available for the 1500s.
GuyW

I’ve got both, on different cars obviously!

I’d always thought the electric fan was the way to go but since rebuilding my Mk1 with a engine driven fan I’m erring to that way. I think it depends on your type of driving though.

My Sprite has always been electric fan but it is a performance car and every bhp counts. It works well, warms up quickly and copes with hot weather - the cooling system is in good condition. It has no manual override and will stay on after ignition is off.

The Midget has the original 1275 plastic fan and that also works well, it takes a bit longer to warm up but copes well at high temperatures. Cooling system is all new so obviously in good condition.

The main thing I have noticed is that high revs with the engine fan is quite alarming in that it sounds like a jet engine starting up! But what I like about the engine fan is constant temperature, once warmed up it stays about the same with only small and gradual fluctuations. The electric fan on the other hand has quite big and quick fluctuations in temperature and I do wonder whether that isn’t great for the engine.

So as usual it’s horses for courses. I’d say on a performance engine or if your cooling system is a bit iffy then an electric fan is probably best. But for a well maintained standard ish car used for general runs in the warmer months there’s nothing wrong with the engine driven setup.
John Payne

So I run a far from standard setup (EFI, supercharger etc) >> what kind of thermoswitch do you use? I consider this one: https://www.americanvolt.com/products/adjustable-electric-radiator-fan-thermostat-switch-temperature-controller-probe
a.o. arnold

I tried using a Kenlowe thermo-switch in the top hose, but I couldn’t stop it from leaking.

I checked the on & off temperatures with a pan of boiling water and then bought a modern thermo switch off eBay and had a boss fitted to the top tank of the radiator.

Something like this

https://www.ebay.co.uk/itm/324734009396
Dave O'Neill 2

I use this one in the top hose:

http://www.demon-tweeks.com/revotec-electronic-fan-controller-243503/?sku=GLOEFC35&istCompanyId=a2904180-3a7d-4e56-b876-cf81c9512180&istFeedId=6fbc4b04-fd28-4ce1-8513-835c8f118690&istItemId=wptppxiix&istBid=t&gclid=EAIaIQobChMIoMr2kvyf8wIVBpftCh0ndQCtEAQYASABEgKgFvD_BwE&gclsrc=aw.ds

I’m on my second one in about 15 years, the first lasted about 8 years and started putting the fan on constant.

You can just about see it in the left of the photo in the top hose.


John Payne

The thermoswitch needs to be reliably accurate, on and off at set figures without too much variation or fluctuation, consistent over a long period of use (many years).

I think the Revotec Electronic Fan Controller, like John and I have, seems fine to me but the difference to on and off is too wide I think. I forget all the figures now but it's all in the Archives.

I have a Revotec (former) higher powered 9" (Blowing, bumper side of rad) fan for my modestly uprated engine (with standard cooling system, no oil cooler) but I'd prefer a 10" Suction (engine side) fan with a controller that switches off sooner.

https://www.revotec.com/acatalog/product_index.html
Nigel Atkins

Well I didn't know that late 1500's and spitfires had viscous fans; at least in the american market.

John Twist even has a video on how to defeat it with a couple of jubilee clips, to erradicate the viscous clutch action, because it seems they fail.

I quite like the idea of a viscous clutch myself, and never had any problems with them on the 3 beemers I've owned in tbe past.


https://youtu.be/mDKIVeibuIo


anamnesis

I never had a problem with the vicious fan on my late model 1500. It was difficult to tell when it was doing it's stuff as it spins all the while in the air flow.

My 1275 has a pre- rad fan which I think I got from a Rover 400. Controlled by a thermostat in a top hose adapter from a Fiesta. It also runs off a permanent live so runs on after the engine is switched off and can also be overridden by a switch should the need arise. In practice, the fan rarely comes on other than occasionally in heavy stationary traffic. Sometimes it will start up for a minute or so as I walk away from the car if I have been for a bit of a blast.
GuyW

I still run the standard system on the Frog albeit with a six blade plastic fan. The system is all comparatively new and I thouroughly cleaned out the block when the engine was apart. I also do not run more than 30% antifreeze in the coolant mix. It copes with traffic reasonably well and this has included trips to Spain and the south of France.
Bob Beaumont

I converted my sprite to a vertical rad, and without a 180 stat it runs too cold in the summer. So maybe I'd benefit from a electric fan too. But I can't really be bothered. Lol.
anamnesis

I converted my 1500 to an electric fan. Never had any real issue with the mechanical one, but it made space in the front of the engine bay for other bits and bobs like the crank position sensor, strut brace etc.

As mentioned, much quieter in normal operation (when not running) but noiser when it is on. Also, with it wired to permenant live it helps cool the engine bay after the engine has been switched off.

Fan switch is mounted in an inline adaptor and is 95 deg on, 85 deg off. Thermostat is standard 82 degrees.

Malc.
Malcolm

Mine's a Revotech too and has never given any concerns.
Stock 1500 engine btw.
I temporarily fitted a telltale light once to find out what it was doing and found it wasn't running much at all, only really in slow traffic after a bit of "exercise".
I've never got around to installing an override switch but I probably will. I trust the fan but not so much the thermoswitch.
Incidentally mine is very quiet running.

Edit: Given that it doesn't do a lot I'd definitely opt for electric vs belt drive. Why waste the couple of horses the belt fan eats if you don't need to?
Greybeard

What is wrong with this?

https://www.americanvolt.com/products/adjustable-electric-radiator-fan-thermostat-switch-temperature-controller-probe

Paying 100,- for a on / off switch for a fan appears a bit high to me
a.o. arnold

Or forget the whole adjustable thingy, only one more thing to worry about and break, and use a simple preset on-off. e.g:

https://shop.stoneyracing.com/universal-thermal-radiator-fan-switch-adapter-kit/

Malc.
Malcolm

If the American Volt is accurate, reliable and has a reasonable expected lifespan then only the probe positioning, I'm not sure about between the rad fins and it depends how thin the probe tube is if going into a hose as some have found coolant weeps when using with (the thicker looking) Kenlowe probe tucked into the top hose.
Nigel Atkins

I have a pre-radiator fan and thermoswitch from a Marina. I learned the hard way that (a) you need a relay or the switch fails, and (b) it needs to be wired through the ignition. One morning the relay stuck on all day and the battery was too flat even for a push start. I think the switch I have is set a bit high as the fan cuts in at about 200, but that's not often. I agree there is a power drain as it takes 10A and the idle drops when the alternator takes the load.
Les Rose

I just soldered a boss in side of radiator and tried a few different temp stats till i got one i was happy with.


mark heyworth

This thread was discussed between 27/09/2021 and 30/09/2021

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