I just recieved a Johnson A419 digital temperature controller, but I think I was mistaken in my expectations. I was under the impression I could plug both a heater and cooler into the controller; however it has just a single plug leading me to assume it can only heat or cool, but not both.

Is this correct? If so what comparable controllers would support both heating and cooling? Also, what is the correct term for each type of controller (single/dual-mode?)?

3 Answers 3


That Johnson is obviously single stage. Try this Dual Stage Ranco. Its already enclosed and ready to go.


The Johnson A419 can both heat and cool. You must open the case and re-position a jumper to change from cooling to heating mode (or vice versa). This requires a screwdriver and no technical knowledge. Be sure to unplug the A419 before opening the case!

Page 7 of the manual has a good diagram on this. While you're opening the case and reading the manual, you should also look into the cut-in versus cut-out settings.

Obviously you would also have to plug in your heating or cooling source appropriately. It's true that you can only be heating or cooling at any given time.

  • I think he wants to heat and cool at the same time, without manual intervention. Commented Oct 25, 2011 at 22:11
  • Yeah, you misunderstand what he wants. He's looking for a dual stage controller.
    – brewchez
    Commented Oct 26, 2011 at 1:43

Indeed the A419 is listed as a "single stage" controller, and capable of controlling a single device. The Love TS2 is a dual-stage switch which can control two devices.

I plan to return the Johnson controller and order a TS2; one trade-off is that the TS2 isn't self-enclosed and lacks outlets, so I hope to build an enclosure similar to the one found at: http://brewing.lustreking.com/gear/tempcontroller.html

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