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DIF PWM Fan Controller Install on S13 S14 240SX

Recommended Tools for Install:

  1. 8mm, 10mm sockets and ratchet
  2. Wire stripper and crimper
  3. Electrical tape or heat shrink tubing
  4. Razor blade or similar tool to separate some stock wiring harness cover
  5. Double-sided tape if desired (3M heavy duty tape recommended)
  6. Ohm-meter/Multi-meter to verify continuity of connections


First Impressions (post install)

I've had a lot of success using the Dual DiF Fan Controller and wanted to upgrade to the latest and greatest new product. I don't care about fan noise (the engine & exhaust are much louder), but I like having the fans be variable speed as opposed to jumping from 0% to 100% when a certain temperature is reached. The cool-down feature and status LED are the icing on the cake.

Old vs New DiF Controllers


I had a chance to test this at a recent auto-x event. I ran several back-to-back laps, which brought the cars temperature up to around 85C (normal under these conditions). With the old fan controller, the fans would be on maximum even though they did not need to be. With the PWM controller, they were on, but only enough to keep the car's temperature down (my guess was somewhere around 60-80%, definitely not close to 100%). During daily driving, the fan is not noticeable, even when it's on.


DiF Controller Close-Up



Since this is an electrical install, disconnect the battery by removing the negative terminal. Completely removing the battery from the engine bay provides more room to work. Next, remove the stock intake tubing if you car has it. This will allow easier access to the coolant temperature sensor on the intake manifold.


It is recommended to intertwine the white and grey wire from the DiF controller together (twisted pair wiring). This will help protect against electromagnetic radiation/noise from other components in the engine bay. One way to do this is to insert one end of the wires into a cordless drill; then power the drill until the desired tightness is reached.


You can refer to the write-up for the DiF Dual Fan Controller install, which is similar. However, note that there are a few key differences, namely in connecting to the fan motors and programming the unit.


This write-up is meant to supplement/complement the included manual, not replace it. Please still read and follow the instructions in the original DiF manual.

DiF Manual Shot



Placement of Fan Controller:

I chose to mount the fan controller in front of the battery behind the radiator support. This location is convenient for wiring and reconfiguring the DiF controller (if necessary). Feel free to mount it anywhere you find to your liking that is away from heat sources.

Test Mount Location for DiF Controller

A small strip of double-sided tape can be attached to the bottom of the fan controller for simple mounting. It is easier to just attach the tape to the fan controller and leave the other side of the tape unpeeled. This will allow moving the DiF controller to a more suitable spot/orientation later during the install.

For my installation, I chose to modify an L-bracket and mount the fan controller with screws to the radiator support

Test Mount Holes Location for DiF Controller

Wiring the Engine Bay:


Electric Fan(s)

Connect the positive wires of the fan motors to the battery. Make sure you use the proper AMP fuse for your fan. Connect the negative wires of the fan motors to the two large white negative wires coming from the fan controller.


Fan Controller

Connect the large black negative wire of the electric fans to a clean chassis ground area or directly to the negative terminal of the battery. If using a chassis ground, it is recommended to sand the area down to bare metal and using dielectric grease, which will help prevent corrosion and moisture build-up.

The large white negative wires of the fan controller should already be connected to the negatives of the fan motors (from above).

Connecting Negative Wires from Fan Controller to Fan Motors

The coolant temp sensor is located on the upper intake manifold near the upper radiator hose inlet. There are two temp sensors in the engine bay - one (1 wire) for the dash, and one (2-wire) for the ECU. The correct one to tap into is the 2-wire ECU sensor.

Sensor wires for DiF Controller

On the KA24DE, it can be identified by a red 2-wire plug held on by a clip. Remove the clip and pull the plug. Once the plug is out, use a razor blade to remove some of the harness cover shielding to allow room for tapping the wires.

KA24DE Coolant Temp Sensor Location

The blue wire w/ tracer is the positive coolant temperature wire. The black wire is the negative coolant temperature wire. Connect these wires to the S+ and S= terminals on the fan controller, respectively. After shielding has been removed, you can either tap the wires with the supplied t-taps, or strip and solder the connection.


Once the wires are tapped, continuity should be verified with an ohm-meter. Place one probe into the sensor plug and the other onto a metal part of the t-tap. If there is no connection, 0 will be displayed; if there is continuity, a 1 should be displayed.


The BA wire for the fan controller should be connected to the battery or other 12v signal. If you don't want the "cool-down" feature, connect the BA wire to an ignition source. The supplied fuse and fuse holder should be used with this wire.


Connect the IGN wire from the fan controller to an ignition source. I chose an orange wire w/ a blue tracer located near the battery. I verified this with a voltmeter.


IGN wire location for DiF Controller

If you want to use the a/c feature (minimal 50% duty cycle fans when a/c is on), you must connect the AC wire to an a/c source. There are a couple of plugs you can tap into near the battery and a/c condenser.


For the manual switch, you will need to connect a switch that is connected to a ground and the MA terminal on the fan controller.


For all connection points, it is recommended to install heat shrink tubing or at least electrical tape to prevent any shorts in the future.

DiF Fan Controller Mounted

DiF Fan Controller Mounted Screws

Programming the DiF Fan Controller:

The fan controller comes unprogrammed. If your fan controller is unprogrammed, it will just show a green light for several seconds, then turn off & repeat the cycle once the car is on.


To program the fan controller, you need to move a few wires around to engage "programming mode."

Rear View of DiF Controller


  • Turn the ignition off. Wait 20 seconds.
  • Disconnect BA wire.
  • Disconnect AC wire if you have it.
  • Move IGN wire to AC terminal.
  • Ground the MA wire.
  • Turn the orange knob to the appropriate position (E for Nissan - this will make the fans cycle 4 times when controller is reconnected).
  • Turn the key to the "ON" position.
  • Reconnect the BA wire.
  • At this point the fan controller should flash the LEDs and pulse the fan(s) to confirm the settings. It will continue to repeat this cycle.
  • After verifying the number of pulses, disconnect the BA wire.
  • Turn the ignition off. Wait 20 seconds.
  • Move the IGN wire back to its original position.
  • Unground/disconnect the MA wire.
  • Reconnect the AC wire.
  • Reconnect the BA wire.


When the fan is working properly, the LED should alternate between green and orange. When it is cooling down, it will flash red.


Configuring the DiF Fan Controller:

The optimal operating temperature for KA’s is approximately 160F to 190F. Since this particular vehicle has a Nismo thermostat installed, which opens thermostat at 143.6F instead of the stock 169.7F, I set the fans to turn on at 158F (letter C) for track days. For stock thermostat, I would probably set it around 170F to 178F, (F to H on the knob).


Testing the Fan Controller:

Once everything is reinstalled and setup, start the car and allow the engine to warm up. The LED should be alternating between orange and green, as described earlier. Depending on your particular setup, location, and weather, it may take a while before the fans activate. A simpler way to test the fans is to use the manual switch and/or set the adjustment dials to a lower setting, so that the fans to turn on earlier.

Wires Tucked Away from Install

Overview of Engine Bay

Shot of DiF Fan Controller Mounted

Various LED status video of Dif Fan Controller:

Hopefully, this video will help some installers recognize the state their fan controller is in. It covers:


  • Not Programmed
  • Programming State
  • Normal Operation
  • Cool-down Feature


Video of DiF PWM Fan Controller in various states