(Adjustable Radiator Fan Relay Controller)

Can be use with any 0-5V sensor signal.

     The AFRCr module is intended to operate a Bosch type automotive relay by switching one side of the relay drive coil to ground, the other side of the coil connects to 12V.  The relay is triggered base on a user selected voltage threshold of any 0V to 5V sensor signal.  As an E-Fan relay controller our module snoops the voltage on the temperature sensor that the PCM/ECM is already using so no extra sensor is required. The temperature sensor can be the standard automotive type that decreases in resistance as temperature increases (NTC) or it can be the PTC type that increase with temperature.   Please specify NTC(standard) or PTC when ordering.

  The vehicle must not change its measuring sensitivity (supply impedance) over the temperature range otherwise the voltage on the sensor will jump and the module will false trigger at some settings. This excludes the GM LS1, but a new LS1 module version is coming soon.  

   In the standard version, the three slide switches on the front of the module set the relay turn on voltage threshold starting at 4.9V and can be adjusted down to 0.1V (in seven 0.7v steps) with a 0.1V turn off hysteresis threshold to reduce relay and fan cycling.  The standard settings are (NTC,4.9V-0.1V, 0.1V hys).  For custom AFRCr modules please specify (NTC/PTC, User adjustble voltage range, turn off  hysteresis voltage).  If you are unsure of how to specify custom module setting just let us know.

The module will flash the switch setting (0-7) on the LED to confirm your settings at power up and upon waking from sleep (only if the switch settings have been changed). During normal operation the module will flash its LED every five seconds, one flash if the fan relay should be off and two flashes if the fan relay should be on. Changes in fan status (on/off) or to new switch settings only take effect at the following wakeup period, which happens every five seconds.

The AFRCr module is Factory Re-Programmable; If you ever need new settings programmed into your module, just email us for a reprogramming quote and Return instructions.


  • Microcontroller based for reliability and accuracy
  • Reverse voltage protection in the event of incorrect power connections
  • Low current (5 - 8mA)
  • Output wire can sink up to 2A to ground (with up to a 3A turn-on surge)
  • Indicator LED to confirm operation and indicate mode
  • Light weight (31 g)
  • Small package (5.4cm x 3.5cm x 1.5cm)
  • Factory Re-Programmable
  • 12 month warranty from date of purchase against manufacturer defects
If you wish to purchase 4 or less modules, you can purchase via Credit Card or PayPal by using the buttons below.  Your order will ship to you via USPS Priority Mail.
If you want to purchase 5 or more modules or would like a different shipping method, please email us (at for a quote. Please include the following in your email - your module selection, quantity and your full shipping address.
For technical questions please email us at