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GUIDE: Installing twin electric cooling fans

craig8585

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I've recently installed a twin electric fan setup on my S15 so thought I would share some information about it.


Originally I used a Revotec Fan Controller to control the coolant temperature, but after doing a bit of research it seems there is a more efficient, more reliable and simpler way of controlling the water temperature. The standard cooling system comprises of a viscous fan with plastic shroud and a single electric fan hidden inside the shroud.

The single electric fan is controlled by the ECU which recieves a temperature reading from a temperature sensor in the cooling system. On the standard S15 ECU the electric fan is set to cut in when the coolant reaches 95C and cut out once the coolant temperature has reduced to 90C. If you have an Apexi Power FC I believe these temperatures are reduced to 90C and 85C. Both systems keep the coolant within a 5C range unless you are cruising at high speed when the temperature will probably reduce to the mid-low 80's (effectively controlled by the thermostat) due to the natural airflow through the rad. The standard electric fan also cuts in when the A/C compressor clutch is engaged.

The Revotec control unit is a good bit of kit, but there have been numerous reports of failure on SXOC and the unit is only capable of controlling the temp within a 10C range (ie. cut in at 95C and off at 85C), which is twice that of the ECU controlled system. Also, there is obviously no provision for the fans to cut in when the A/C system is engaged.

Therefore I devised a very simple system that utilises the standard ECU fan control, but is also able to power a higher ampere twin fan setup safely (see diagram below). It is necessary to use a relay in the system as the twin fans will draw more current than the original single fan and would probably blow the fuse. Most aftermarket fans are around 80W each, which works out at 18A for the pair. It is important to use a relay and wiring etc. suitable for the job, so I used a 30A setup to be safe, with a fuse incorporated into the relay.








Hope this helps guys. It will also save you buying a Revotec controller :)

If there are any points I have missed out, please add them below. I'll add some pics up as soon as I can too.
 

DeanS15

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nice guide mate, did you fit these with a shroud or something from apex? if so could we have a pic of it fitted ;)
 

craig8585

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Yeah, I've fitted mine with the apex shroud and I helped James LuPix fit his last night too, but he didnt have the shroud so ghetto's them on with cable ties!! :D

I'll get you a pic at the weekend mate as the car's at home and I'm not. The apex shroud does look good and fits well, but the quality of the fans that come with it defiantly aren't as good as the Driftworks ones.
 

tooley

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Good work craig i didnt see this yesterday i hardwired mine to the a switch in the dash. I was going to post up today to see if the s15 had a stock thermostat etc. lol

MY s15 didnt have a single fan however the loom is there for one. So where do i get the relay from maplins?
 

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30A fuse plus relay were both from Halfords and I believe Craig said it's the older style 'larger' fuse.


Many thanks to Craig for helping me install this exact setup :) I bought a couple of 12" Japspeed fans to attach to the 50mm Japspeed rad already fitted a couple months ago... They didn't come with mount/bracket/shroud so we just ended up cable tying them to the rad and it's not going anywhere - tight as feck :thumbs: so I'm happy :D

Fans kick in dead on 90 deg and turns off when it drops to 85. Takes less than a minute - awesome amount of air being sucked through lol!!
 

craig8585

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Yeah, the fused ones are £8 from Halfords. You'll need some electrical crimps and the crimping tool and some insulation aswel to do it neatly ;)

No probs James, pleasure as always! :D
 
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did you remove the standard viscous fan completely then? only using the twin fans?
would this be fine to use as theyre not running all the time, and only kick in at certain temperatures?
 

craig8585

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Yeah, I binned the viscous, theres no need for it at all with this setup. The viscous fan is inefficient as they run all the time, even when your engine is stone cold and when you've got enough speed to not need a fan. The twin fans suck an incredible amount air through the rad too.
 

LuPix_S15

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Yup it only takes about 30 secs IIRC for my twin fans when they kick in to lower water temp from 90 back down to 85 which is when they turn off - that's with the car stood still!!
 
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quality! they look a lot better too and tidy the bay up a bit :D
i'l have a look into it once i get my other problems fixed :D
 
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Is there any way of wiring sequential fans? i.e. a single fan kicks in at 90deg. If the temps keep rising to 95 then the other kicks in. Not sur how this could be achieved though. This would keep the water at a more constant temp. Short of fitting an electric water pump kit, like from Davies Craig.
 

craig8585

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Those electric water pumps sound like a good idea but would be too much work for me.

Well, you can use the standard thermostat/fan control to make them kick in at 95C, but you would need another controller to kick it in at 90C. In an ideal world I'd have the first fan kick in at 85C (off at around 83C) and the second on at 90C (off at 85C). HKS used to make a fan controller unit but I think it's discontinued now. Going to have a look around now, theres got to be something that will do this properly!
 

craig8585

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Found something!

This gets wired into the original water temp sensor that feeds a signal to the ECU. You set it at exactly what temperature you want the fan to come in at and when you want to cut out - link to instruction manual. If you want them to come in seperately then buy 2 of these and set them at different temperatures. May have to try one soon :)
 
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tripleJs15

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Not familiar with the Apex shroud, can someone clarify and/or post some pics ?
 

craig8585

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Did you use the one I just posted above? If you bought it in America can you remember where you got it from? I can only find it in one place in the UK and they are £90 each delivered!! I'll post pics of the Apex fan shroud for you as soon as I get chance!

I've been thinking about it and for the cost of 2 of those units above I could buy the HKS fan controller which allows you to control both fans independently, or both fans simultaneously at different speeds - both of which would be ideal. I've just called Apex Performance to see if they can get hold of them.
 
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tripleJs15

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The distributor is frsport.com, and it let's you control each fan independently of each other. I ve seen them cheap on Zilvia.net.
 
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