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.
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.
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
Edit. Added a wiring diagram for these units.
Finally, some notes on programming
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.
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
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.
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.
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
Edit. Added a wiring diagram for these units.
Finally, some notes on programming
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