2008 MS3 Radiator fan

Uberfly

Uberfly

Greenie N00B Member
Anyone know of radiator fans that will work with the Mazdaspeed 3s? looks like regular mazda fans are $100, and MS3 one is about $450.

I troubleshoot my fan down to the controller. seems like it was not passing ground to the fan itself. I also verified i was getting a control signal and validated the Fan Duty Cycle was above 0% with accesport while probing the control line.

Thinking about getting a regular 3 fan and seeing if i can swap it into my MS3 shroud. Has this already been attempted?
 
I cant speak for the regular 3, but the MS3 has a 3 speed fan and uses a switched ground to turn on and off. Meaning there should only be a ground signal going to it when the fan is running.

What symptoms are you experiencing?
 
Mauro_Penguin said:
I cant speak for the regular 3, but the MS3 has a 3 speed fan and uses a switched ground to turn on and off. Meaning there should only be a ground signal going to it when the fan is running.

What symptoms are you experiencing?
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Using the AP, I monitored coolant temp get up to 225 with the fan not turning on at all. That's the main symptom. I'm reviving this car from sitting for 3 years, so it's not as if it was working last week and just started running funny. Lots of electrical gremlins.

While the car was at 225, I checked fan duty cycle on AP and saw it was at 30%. I disconnected the fan and probed the control line (my understanding is it's PWM to get the multimodal speeds) with a DVM on mV scale and saw it was high (I believe 7.7V). Turned the heat on full and let the engine get down to 199, verified fan duty cycle was reading 0% on AP, and that control line was now showing 0V on DVM.

Once I verified control was sending a signal, I removed the fan and shroud, reconnected everything on the top of the engine.

I then let the engine get hot and verified there was a duty cycle on the AP. I took an led test light and connected to positive terminal in battery. Pierced the negative cable going into the controller and the test light lit up. I then checked the case of the controller (it has a metal case with another green wire and do-hicky connected to the case) and it did not light up the test light. I checked the output ground of the controller to the fan, and it did not light the test light.

If I short ground to the fan directly, it will spin. Seems like it's the controller to me, which doesn't seem to be sold separately.


ETA, I would agree with switched ground, but I believe it's controlled by the fan controller, which is regulated by PWM to get 10, 20, 30%, etc. So that controller had three wires in, two out. Three in being 12V, GND, and some control. The controller determines the fan speed and the output ground is controlled depending on what's being dictated by the controller.

At least that is my understanding. Happy to get corrected if I'm off in left field
 
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