Thermo Fan Controllers

Had a rough few days tweaking the Dakota Fan Controller, just didn't want to run correctly.

The Dakota has the ability to use any temp sender, including the stock ECU sender, unfortunately the Dakota didn't want to work with the Nissan one. So I had to install a dedicated sender, thought this would make everything work smoothly but I was very wrong...

What was happening was that the Dakota was too sensitive and picking up slight temperature fluctuations. For example, my PowerFC would show a readying of 80-82C and the Dakota was showing 80-88C. Strangely, this didn't show up when testing the senders externally from the engine. Because the Dakota temp sender is physically small, it heats up and cools down very easily. So in an enviroment with high water flow and slight temp fluctuations, the Dakota was cycling the fans on and off randomly. Not something you want...

After numerous emails with Dakota, we weren't able to find a solution. Which is a shame because it's such a good product! I decided to move on and try find another dedicated fan controller, but there was nothing out there that could use the Nissan sender as well as control the fans they way I wanted.

Then I came across DIY kit sold at JayCar:

Read more after the break...

What it does is monitor a voltage signal, the ECU's temp sender in our case, and triggers a relay when it reaches your set voltage. It can be configured to trigger from a low-to-high voltage, or high-to-low for temp senders. So as the temp increases, the voltage signal drops.

Went to JayCar and bought a kit and built it up within 30 minutes, it has very few parts and everything is supplied. Not bad for $32.95.

Did some initial testing and everything works well. Everything is triggered correctly according to the ECU temp reading. When driving on the highway, the fans are never on. Fans are rarely on when your driving around town, and sometimes turn on when you're waiting at the lights. They also don't stay on too long, just enough to drop the temps to 80C.

All parts in the kit.

I like to solder all the low profile components first.

All completed and testing phase.

Once you've set the trigger point to turn on the fans, you need to set the off trigger. This is called the hysteresis setting. It determines the voltage difference between ON and OFF. Unfortunately the standard kit doesn't give enough adjustment so the temp would drop 10C before the fans were turned off. I had to modify the circuit a bit by adding a 1Mohm resistor in series with the hysteresis trimpot. Now the fans are turned off once the temp drops by 4C.

Modifications to circuit to allow more hysteresis.

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