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Discovery 2 Mechanical to Electric Cooling Fan Conversion

Discussion in 'Members Vehicles/Projects' started by willston, Apr 16, 2018.

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  1. willston

    willston New Member

    Apr 14, 2018
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    Ontario Canada
    Full disclosure: I'm a geek

    My clutch fan was going, and trying to get one where I live is very expensive right now so I decided to give the Rover a 2018 upgrade to electric cooling fans. Doing so I wanted to accomplish a few goals:
    1. Gain cooling efficiency
    2. Gain a bit of power back
    3. Quiet the engine bay a bit
    4. Make it reliable
    5. Make it generic, with parts you can buy pretty much anywhere or keep in stock
    Traditional electric fan controls drive me crazy. They suddenly click on full speed and back off, its almost archaic. The only way I could get around this was intelligent control circuitry. I got myself an Arduino, a few high power MOSFETs, some thermistors, some perf board, fuses and got to work.

    Choosing fans:

    I chose to go with 6 7" fans. Why? Redundancy and coverage. On the small radiator of the discovery I have 6 fans covering the majority of the surface, and with 6 fans the likelihood of all of them failing at once is very very slim. These fans are also pretty generic which means if one does fail, I can source one easily. Each of the fans I choose is around 75 Watts, and they move A LOT of air.

    Mounting fans:

    I removed the lower fan shroud and old clutch fan and then cut a piece of 1/8" aluminum to be the same dimensions as the radiator cooling area. This allowed it to slip in between the inlet and outlet hoses and lean on the aluminum frame the tanks are attached to. The fan plate is supported by the vehicle frame (with rubber vibration absorption) at the bottom, then I secured the assembly to the radiator. This whole unit is then covered and given extra support by the upper fan shroud.

    Control Circuitry:

    Okay, so my fans are a little overkill and nowhere near as efficient as the clutch fan when all are engaged at full speed. What I decided to do is control the fans speed using PWM. Measuring the temperature off the engine, from the rad inlet and outlet I detect once the engine is up to 80ºC and then the fans come on (100% duty for 500ms to spin them up and then drop to 40% power). The power then ramps up to 100% when the coolant hits 100ºC and varies between 40% and 100% depending on the temperature. This way I can detect the cooling efficiency of the cooling system.

    I used 3 25amp MOSFETs to control the fans (each has its own fuse), breaking it up into twos (2 fans are on a MOSFET) and a killer capacitor bank to keep all the AC generated from the PWM at bay.

    The last thing I did was read the voltage off the battery. This is how I determine if the vehicle is running or not. When the voltage goes above 13.5VDC the system becomes active. Because the system is always active (I'll explain why) I wanted to have a warning to someone under the hood that the system could turn on. As soon as the system is enabled, I play a small chime through the fan motors to alert that the system is active. 15 seconds after the chime, the fans will spin up if required.


    When you start the car, the voltage stabilizes after a few seconds and a start up chime is played. If the vehicle is warmed up or getting warm the fans will start working to try and keep the temperature as low as reasonable.

    When the voltage is lower than 13.5 volts the system will remain running for 30 seconds (extends out to 5 minutes if temperature is higher than 100ºC) and then wind down the fans slowly, playing a small exit chime alerting you the system has been deactivated. The chime differs based on the shut down temperature so that way I know roughly what the temperature is when I'm walking away. If it is constantly higher than 95 I need to take a look at it... so its a silly thing but it works.

    Just incase my circuitry fails, there is also a jumper I keep in my glove box which hard wires them on in 3rds.

    All in all the project took my 4 hours, and all I had to order was fans so I didn't think that was too shabby. It also cost me just under $200 CAD and I didn't have to pay any import tax or duty :). Its been working solid for 6 months now.

    I'll post pictures later.
    Trailstar and 300bhp/ton like this.
  2. rob_bell

    rob_bell Well-Known Member

    Jul 18, 2016
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    Sounds very interesting: look forward to the pictures! :D
  3. Goc3k

    Goc3k Well-Known Member

    Dec 3, 2017
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    I was awaiting the pictures in the introduce yourself section. Sounds kushty!
  4. JUKE179r

    JUKE179r Well-Known Member

    Jul 5, 2018
    Likes Received:
    Suffolk County
    I guess no pics, eh? :(
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