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MG MGA - Fuse for twin electric fans.

I am about to begin the process of fitting two electric cooling fans to my radiator and I have been getting the last few things together so that I can get started.

The last thing I need to do is to decide which size fuse to use in the power supply.

Today I connected one of the fans to a spare 12v battery through an ammeter to see how much current one of these fans draws when running.
The current very quickly stabilised at a little over 5 amps but I was a little surprised to see that the current draw spiked at between 11 and 12 amps on start up,just for a fraction of a second.

I had intended to go for a 20 amp in-line fuse for the supplying both of the motors but I wondered if the split second spike of approx 24 amps would actually blow it.

I would prefer not to over fuse the supply but any thoughts on whether to go for either a 20 or a 30amp fuse would be appreciated.

Cheers

Colyn

PS I have already fitted an alternator to help cope with the extra load.
c firth

Hi Colyn
A long time since I have posted but me and the car are still around!
I think you just need a slow blow fuse to "ignore" the spike. But the experts will no doubt advise if this is correct or not

Regards, Graham
g Victors

Thanks Graham

I finally got the twin cooling fans fitted today and I decided to go with a 30amp fuse to start with.

The fans ran fine and when I checked the fuse it didn't show any sign of overheating.
So I am confident that a 30 amp fuse will cope well with the load.

Colyn
c firth

Colyn..What arrangement did you use and what fans? ..do you have a pic? I have been operation my twins for a number of years and the system works well. I am away from the car elsewhere in Oz right now but will look at the fuse when I get back home in a few days.
Neil Ferguson

Hi Neil, good to hear from you again.
I finally got around to fitting the twin radiator fans that I have intended to do since reading about your project about 4 years ago.

I used the same type Davies Craig 9" fans that you fitted to your car, they fit the MGA radiator as if they were made for it and so far it looks as if they are going to work really well. I secured them with some special spring-loaded pull-through fixings which seem to hold the fans really tight against the rad. These feel so secure that I didn't use the extra bolts that you fitted through the radiator flange.

So far I have only tested the fans with the car ticking over but, even so, I was really impressed with the way they cooled the engine.
The fans came on at 195 Degrees F and you could visibly observe the temperature gauge dropping to 165 degrees when they cut off after a couple of minutes running.

I am looking forward to seeing how this set up works when I run the car over the summer.

I have been trying out a single fan since last autumn, a 10" Revotec fan which seemed ok but I always felt that it didn't cool enough of the rad.

I found that, whilst driving, the car generally ran 10 to 15 degrees warmer with the Revotec fan fitted than it did with the big plastic fan I had been using for a couple of years previously.
I wasn't too concerned about the raised running temperature but I just wanted the fans to be able to keep the temp under control when the car was ticking over.

I did take some pictures but I forgot to bring the camera to work today, will post some later when I get home.

I plan to run the car as much as I can over the next couple of weeks and I will let you know how it goes.
I may even do a proper write up of the project for everyone to be able see how it went and avoid the pitfalls along the way.

(for example, I took the fresh air pipe out of the space in front of the rad to give me more space to work with when fitting the fans. The I found out that with the two fans fitted, there just wasn't enough space to get the pipe back through to refit it.
In the end, rather than remove the rad all over again, I opted to take out the grille which was another story altogether!)

Will let you all know how the fans work out

Cheers

Colyn
c firth

Colyn

Just out of idle curiosity what is the history of your radiator? With the current Spring temperatures in the UK my temperature would not go above 175 sitting at idle while I retuned the carbs. Even on my long run a couple of weeks ago in the slightly warmer temps we had, it would not go above 190 in the hour of queuing.

I still have 'my thing' about owners addressing the symptoms rather than investigating the cause. Bit like putting a plaster on a cut on your toe, while blood spurts out of an artery.

Steve
Steve Gyles

Hi Steve
the rad I believe is a Bob West one, now about 6 years old and like with your car, overheating has never a problem.

When I fitted the big plastic mechanical fan 3 years ago it brought the running temperature down from 180/185 degrees to around 170/175 degrees but the noise it made at higher revs has always got on my nerves. It would go up to 190ish in traffic but no higher.

When I fitted the single Revotec 10" fan I noticed that the running temperature went up by 10 degrees which I think shows that the plastic fan must still have been cooling the rad even when the car was being driven.
(I have long thought that the airflow through the engine compartment must kind of stall at higher road speeds and that the mechanical fan may still be the main cooling force in the car)

I suppose the only way to know for certain is to run the car a distance without any fan at all and see how hot it runs.
I would bet that it will run hotter without any fan than it does with a mechanical fan fitted.

I hope to drive the car over the weekend to see how the twin fans cope.

I hope that ideally they should only begin to operate when the car is idling in traffic but I have a feeling that they may well also operate when the car is being driven hard up hill or on a high speed run etc.
I suppose this only replicates how the mechanical fan works.

It looks so far that the twin fans can easily control the water temperature of the car at idle and I have noticed already that they seem to have cured the lumpy tickover that always happened in traffic when the under bonnet temps were getting really high.

I just need to run the car for some distance now to see how things go.
Im quietly confident about the set up so far, but not confident enough to leave the big plastic fan behind in the garage just yet :-)

Colyn

c firth

Steve,I have just re read my last post and I don't think I was very clear when I said that the twin fans were cutting in at 195 degrees with the car stationary and the engine ticking over.

My car (like yours) would never get to this temperature before with the plastic engine driven fan fitted. Maybe it would creep up to 190 in traffic and occasionally if I thought I would be stuck in traffic a long time, I would put the heater on to help the cooling system out.

But now, with mechanical fan fitted, the engine warms up much quicker and I chose to set the thermostatic switch to cut in at the higher temperature of 195 degrees. (obviously with no fan fitted at all, the coolant would just continue to heat up until it boiled)

I am going to experiment with the temperature the fans cut in at to see if I can manage to adjust it so that they only operate when the car is stationary.

Will let you know

Colyn
c firth

Colyn

So you have put a tourniquet on a leg that was not bleeding!! :-)

Steve
Steve Gyles

Belt and braces, Steve! We all do it. Shane
Shanerj

Looks like you got me there Steve,

it wasn't broke but I still went ahead and fixed it anyway! ;-)

Will just have to see how it all works out.

I will try to upload a couple of pictures of the fans

The first one should show how the twin fans compare with the pertronix single fan


c firth

Picture of fans on radiator from the front


c firth

Another view of the fans on the rad looking from the grille.


c firth

View from above showing fans and thermostatic control in the top hose


c firth

Oops!
just noticed that I wrote "how the twin fans compare with the Pertronix single fan"!

For "Pertronix" read "REVOTEC"!

(Pertronix do electronic ignition, distributors and coils etc but not fans as far as I know)

Colyn

(It's a pity that this forum won't let you edit your posts retrospectively, it would be useful for someone like me as I tend not to notice my typos or mistakes until a day or two after I have written them!)
c firth

This thread was discussed between 22/04/2014 and 26/04/2014

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