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Discussion Starter · #1 · (Edited)
After an overheat when stuck in traffic with the A/C running I found my main fan controller was dead. It was quickly fixed using a small Tyco relay that I mounted inside the fan controller housing, driven from the ECU it switches the fan directly replacing the overly complex and problematic electronics.

Sorry in my haste to fix it I didn't take any pictures but here is the circuit modification:


To get inside the controller simply lever up the 3 metal tabs on the controller cover (that are folded over heat sync) and carefully lever off cover. There is space inside for the relay if you cut away the plastic between the two 100mmF capacitors. Araldite the relay into position as well as the new wires to make it vibration safe.

Points to consider if doing this mod:
1. The main fan will be full on when requested from ECU rather than variable like with mitsi controller - however my Vipec ECU is configured to use the A/C fan as the primary radiator cooling at 90 deg and the main fan as secondary when temp gets to 94. This means main fan will tend to switch on/off and not be on all the time hence I'm not worried about it working too hard.

2. Either make sure existing electronics is open circuit or disconnect the existing pins to avoid any problems from it especially if the fault is that fan is permanently on.

3. I left the smoothing circuit in place to filter any noise from the motor.
 

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I know this is an old thread but I'm not willing to pay Mitsubishi £180 for a nwe controller as I stupidly threw mine out :)

The relay you seem to have 2 lives going to it or is the signal from the ECU an earth?
 

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Discussion Starter · #5 ·
The controller must be short circuit internally (or hopefully not the ECU output is wrong). First disconnect the guts of the controller board from pin 2 on fan connector and see it that helps. If not disconnect controller board connection to pin 2 from ECU connector.

I had to do this on mine.
 

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Discussion Starter · #7 ·
If you disconnect the ECU plug does the fan go off?

If not then you must have a wiring error?

If it goes off with ecu disconnected then that say new relay is good but means the ECU is always asking for fan (ie the output is always pulling down to ground).

I have a E7 so wiring is very similar otherwise.
 

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I've fitted standard 12v 30amp relay.

Wired like so
Pin 30 = ignition live
Pin 87a = to fan live
Pin 86 = to ecu signal
Pin 85 = to live
 

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Pin 87a is Normally Closed (on with no power to relay).

You need to wire pin 87 to fan +ve NOT 87a...
 

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When I checked with Evoscan I seemed to be getting a ground to earth when ignition on and then when fan activated it went off.

But not it doesn't matter which way I do it
 

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TD's original post showed a good bodge, aka improvisation :), to "repair" a fan controller, but it will only work with an aftermarket ECU.

The OEM ECU outputs a variable frequency signal to the fan controller and hence varies the fan speed

Send the same signal to a relay and who knows what will happen :confused: , running the fan continuously the safest option :thumbup:

TP your options are;

Buy a new controller - Ross Sport were selling them for c£50 iirc
Fleabay have/had some pattern units from Taiwan
MLR vulture traders :thumbdown
New from a dealer :eek:
Ask a "geek" to flash your ECU

Grant :)
 

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Discussion Starter · #13 · (Edited)
I was indeed using an aftermarket ECU. Does anyone know the drive freq/mark space characteristics from OEM - I bet an odd extra component or two would make it work :naughty:


TP - if you disconnect ECU does the fan go off?
 

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Better not post it on here though, the Mitsubishi police will swoop.

I'll just fit a switch and control it myself, or fit a temp sensor that I can get to control it, mine is mostly a track car anyway.

I'll check tomorrow and see what happens when I change wires and disconnect things.

Thanks for your help TrickyDick
 

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Can you splice the AC clutch wiring for you relay, so basically when the clutch is on, the relay will turn the fan on.

If you can get a controller for £50 I'd just put one on..
 

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Its an electric fan with an alloy radiator so fan on full don't matter.

Aircon stripped out so wiring can be cut or bodged to my hearts content.
 

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Well I'm feeling a little bit silly now :)

Although it was pointed out it is a negative signal from ECU my brain ignored this, I still connected the negative to the other side of coil.

And it is 87a I had to connect to as the ecu drops the signal when activated so coil permanently engaged unless fan on.

I have controlled it with Evoscan to activate the fan, and weather I switch low speed or high speed my fan switches on.

Thanks for your help TrickyDick saved me a good few pounds
 
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