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PWM Fan Control
#1

I saw somewhere that the MS3 has PWM output to control the radiator fan.

Anyone here using an ECU PWM to drive any substantial fan, the radiator or interior heater fan?
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#2

You don't drive the fan with the ECU's pwm output directly.  You use either a solid state relay, or get a fan and controller off something like a newer volvo or crown victoria.  The ECU's PWM outputs are good for 2 amps tops.
86 Mazda RX7, 2.3 swap, t5, MS3 sequential, BW EFR 6758
"If you can't dazzle them with knowledge, baffle them with bull sh*t"
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#3

Good point.

In fairness that is why I said "control" rather than drive, but in a forum it shouldn't be left unsaid.

Right now I have a set of relays that reverse the signal from the LA3 to do a dual speed control of the radiator fan.

It would be easier, in my mind, to simply use a PWM signal and PDM (or just a driver) to do a variable control of the fan. Then it could gradually speed up as needed to overcome a temperature differential or A/C line pressure issue. It could also power down at speed and let the wind velocity do the work.

But other than programming a speeduino to do this, I don't know if the PiMP knows how to do this trick or can be taught it.

Either way, thanks for the reply.
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#4

(09-08-2021, 03:58 PM)Desert Patina SVO Wrote:  Good point.

In fairness that is why I said "control" rather than drive, but in a forum it shouldn't be left unsaid.

Right now I have a set of relays that reverse the signal from the LA3 to do a dual speed control of the radiator fan.

It would be easier, in my mind, to simply use a PWM signal and PDM (or just a driver) to do a variable control of the fan. Then it could gradually speed up as needed to overcome a temperature differential or A/C line pressure issue. It could also power down at speed and let the wind velocity do the work.

But other than programming a speeduino to do this, I don't know if the PiMP knows how to do this trick or can be taught it.

Either way, thanks for the reply.

I'm dealing with the same problem ..I know the amps from pcm are not enough to power the fan and I was planning on using a couple fuel pump relays to activate mine ?..Will this work and I see where you said you have yours reverse the signal ? Could you explain this ???...Also I was considering RON FRANCIS wiring for input
I don't know what this is ?
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#5

These are the sort of questions that belong on the PiMP support forum. That's where they will get answered the best. We don't spend hardly any time over here.
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#6

No worries, I've since found that a car PDU can handle the fan work, and I think I'd rather just use that rather than the ECU.
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#7

(09-12-2022, 08:59 PM)Desert Patina SVO Wrote:  No worries, I've since found that a car PDU can handle the fan work, and I think I'd rather just use that rather than the ECU.

What is it, PDU? Reference or part number? I am curious about it.
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#8

with my pimpxs im using a jeep Cherokee fan relay to control my fan. works great. bring on my sn95 soft and float it around 50% unless it is really heating up
Function before form. Going fast is looking good!
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#9

I ended up using the stock fan circuit that came with the XR4Ti s.a engine harness. The grounding switch was at 226 which I felt was too high. I bought a 195 on 185 off switch and installed it along with a 180 thermostat....works great
I don't know what this is ?
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