PWM Fan Control

Mustang5L5

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I know this has been discussed elsewhere and isn’t anything spectacularly new, but recently I did a little playing around with this and made a few videos.

There's a lot of OEM fan controllers out there that can be used with various ECU's. I got my hands on a few but settled on one that I was able to get very cheap. It's a VERY common controller so you should be able to snag one in the junkyard. I got three on Ebay for under $20 shipped with wiring.

I'm using this style controller which came on a lot of Mazda's, Mitsibishis, Infiniti/Nissans and possibly more. In addition to being cheap, it also has two fan outputs. I've seen this wired on dual and single fan setups. on single fan, the two outputs are wired in parallel to the single fan motor. This controller can withstand up to 50 amps. It also has a soft-start feature, which really helps control current. I measured 25 amps max on my contour fan setup and use a 30A fuse with 10G wiring.

1643923316618.png

Anyway, this video shows what it can do. lot of this would apply to a lot of the other various fan conrollers like the fusion/corvette controller or the various Bosch units on a lot of Mercedes/Volvos. This could also apply to setting up a fuel pump or anything else that uses PWM control


View: https://youtu.be/N-o8yFmQQgo



One thing to note. The Amazon controller i used in the above video outputs a high side PWM signal (PWM+). My Megasquirt uses a ground-sink type of PWM signal (PWM-) . So the duty cycle range i used in the above video didn't work for the MS3X. I actually had to invert it.

Some more info here.


View: https://youtu.be/XrXb13uJiq4



One thing to note, the OEM wiring supplied on these modules in pretty robust. I beleive it is 10G wiring to the controller (18g pwm wire) and 12-14G out to each fan. I purchased an aftermarket harness for it and that wiring was smaller. 12G main feed and 16G out to the fans. Depending on your fan, this may or may not be adequate. There are aftermarket versions of this controller out there with harnesses for under $30. They don't have the greatest rep. Search around on ebay and you might find a good deal on a OEM unit. Like said, i purchased 3 with wiring for under $20 on ebay.

Here's your proposed wiring diagram shared by tjm73 on corral.net. One thing to note is the relay on the main 10G feed wires. The reason for this is to turn power off to the controller when the vehicle is shut down. This does two things. #1 it prevents potential backfeed to the ECU, but more importantly it prevents the module from going into "failsafe" and speeding up to max RPM. The modules are designed to do that when they lose the PWM signal from the ECU. The thought it to default to fan on to prevent overheating. So, if you don't install the relay here, the fan will go to max speed when you turn the vehicle off.

1643924018306.png


One final note specific to megasquirt. Right now the fan control only has on/off relay capability and you must build a PWM Generic output A for this based on coolant tables. I'm told the latest Beta on Tuner Studio will allow for PWM fan control to allow more fan control with regards to AC on, TPS and VSS settings
 
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nickyb

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Not having a Megasquirt , or term x and wanting to use this setup, the trigger wire from terminator x going to pwm ,is it possible to use a temp. Switch and the a.c. Wire to trigger ?
 

Mustang5L5

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Not having a Megasquirt , or term x and wanting to use this setup, the trigger wire from terminator x going to pwm ,is it possible to use a temp. Switch and the a.c. Wire to trigger ?


It needs a PWM signal for full range control.



However in the video you’ll notice when i ground the PWM wire, the fan turns off, and when I disconnect it completely it goes to full speed.

If you put this wire on a relay and made a connection to ground, and then broke it, you could alternate between off and full speed, with the soft-start feature.

Not really the proper intended use of the module, but it would work.
 

nickyb

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So if I use the Volvo module and a BMW temp switch I'll have just low and high,not soft start?
 

Mustang5L5

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So if I use the Volvo module and a BMW temp switch I'll have just low and high,not soft start?

Just so I give you the right answer, which Volvo module are you talking about. The 2-speed one? Or the pwm module?
 
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Mustang5L5

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,the two speed,and what BMW temp switch?

Very good write-up here with part numbers and such.



Here’s the 180/195 temp switch. There is also a 195/210 switch
Temperature Switch in Radiator 80/88 Degree for BMW FACET 61318361787 Amazon product
View: https://www.amazon.com/dp/B075GJT7WG/ref=cm_sw_r_cp_api_glt_i_FKKSR5PFV8H4QQF0K77A


You need a m14 female to 3/8” npt adapter for the bmw switch.


You need an actual 2-speed fan with low and high windings, or a resistor pack like the contour fan. The relay itself won’t output two speeds.
 

nickyb

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I'm looking at contour fans with resistor , will this be soft start of not ?
 

nickyb

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Thanks, I'm just worried about the spike when it turns on high.
 

Mustang5L5

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Thanks, I'm just worried about the spike when it turns on high.

The spike will be less going from off to low, and then from low to high, than it would be from going from off to full speed.

As long as your wire size is appropriate and you use a slow-blow fuse, it should be fine.
 

nickyb

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That sounds ok to me, I'm just planning now as I have been running my blackmagic fan for years now and figure it's time to upgrade.
I'll go to the pic a part and grab the relay and all the connectors I can,with as much wire as I can.
 

KRUISR

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I 100% agree with Mike on the low amp jump going from off to low speed and low to high on the Contour fans.

If grabbing a Contour Fan at pic a part grab as much of the wiring harness back to fuse box (with connectors if you can). Don't forget the Mystique and FWD Cougars are the same fan with the thermoresistor. Personally whenever I grab a Contour fan at wreckers I always take the wiring back to at least the closest connect to the fuse box, some times I take the fuse box as well (gets me fuses, relays, connectors and a mount)

Video I made at the wreckers showing what wires you want and what they do on the Contour harness at the fan.

View: https://www.youtube.com/watch?v=MmYFLhR12b8&t=4s
 
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KRUISR

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Question on the set up you have above. What would the output from a resistor pot do as the input on the controller module (where you have Term X input shown)?

As you turn the pot you would get differing voltages. Or am I not understanding the input signal properly?
 

Mustang5L5

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Question on the set up you have above. What would the output from a resistor pot do as the input on the controller module (where you have Term X input shown)?

As you turn the pot you would get differing voltages. Or am I not understanding the input signal properly?

It wouldn’t work.

The signal it’s looking for is a specific frequency range and square wave duty cycle. It’s the duty cycle that controls how much the fan operates such as this signal
58EA2412-1B6D-4242-8A9D-8B3905E6B97B.jpeg

With the resistor pot, I’d imagine you’d get an off with low resistance to ground and at some point it might trigger on when the resistance decreases. But it’s not the proper signal (or lack of) and would give you off/on at best. Would need to test however.

This is the unit I used to test it, and how it’s temporarily setup on my car until I actually put the MS in. Set the frequency to 150-300Hz, and then turn the knob to adjust the duty cycle and control the fan

Frequency Generator, DROK DC 3.3V-30V 5-30mA 1Hz-150kHz Adjustable Output PWM Pulse Duty Cycle Square Wave Function Signal Generator Module Amazon product
View: https://www.amazon.com/dp/B07P848DYQ/ref=cm_sw_r_cp_api_glt_i_E7S4AF7RXZ3XX8YCBP6F?_encoding=UTF8&psc=1
 
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hoopty5.0

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These temp switches - are they meant to be used inline on a ground or a + voltage application?
 

Mustang5L5

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Say I was going to just use a simple temp switch, like the amazon link above?


Depends. Some temp switches ground through the case, so they will just have a single wire out. Some have 2 wires out, where you connect one to ground. In both cases, the other wire connects to the ground side of the relay you are activating, and you supply 12V to the coil in the relay. These all work on the grounding leg.
 
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