Skip to product information
Johnson A421 Digital Temperature Controller
  • Johnson A421 Digital Temperature Controller
Johnson A421 Digital Temperature Controller

Johnson A421 Digital Temperature Controller

SKU 41944
$274.99
Eligible for Free Standard Shipping Details

Product Details

Ideal for keeping the temperature controlled during fermentation, the Johnson Digital Temperature Controller overrides the internal thermostat, keeping the temperature exactly where you set it in either a heater or freezer. A must for homebrewers wanting more control over fermentation. Easy installation, just plug the controller into an outlet, then plug your appliance into the controller.

External overriding thermostat with backlit digital display. High and Low Temperature Stop Values determine whether the unit is heating or cooling. There is no longer a need to open the unit to switch between heating and cooling modes.


  • Use to heat or cool a fermentation environment

  • For use with a refrigerator or freezer, it operates compressor when ambient temperature rises above your programmed temperature

  • For use with a heater, it activates when the temperature drops too low


  • New! Backlit display for even easier-to-read display


  • New! Faster Programming with three-button interface


  • New! Internal defrost settings

  • Sensor probe monitors the inside temperature while the easy-to-read LCD display shows it in either Fahrenheit or Celsius

  • Includes 6’ extension cord with plug and 6’ sensor leads

  • No additional wiring for installation is needed

  • 120 VAC line voltage

  • Range: -40° F to 212° F

  • NEMA 1 enclosure, suitable for dry environments




California Proposition 65

⚠ Proposition 65 Warning: This product can expose you to chemicals that are known to the State of California to cause cancer and birth defects or other reproductive harm.

Additional Information

Support Documents
Click here for documents
Support Documents — Instructions
Click here for instructions
SKU

41944