Ranco customizing question

I have two Ranco single stage controllers. I recently purchased a two stage controller for my ferm chamber so now I have an extra.

I would like to have two single stage controllers use the same temperature sensor so I can have one control for cold and the other for heat. I tried wiring both ETC units to one probe but I get strange readings. The temperature should have read 65, but when I plugged in both controllers, one read 39 and the other read 41. If I unplugged one controller, the remaining powered one read 97.

From some reading on another board, I think one ranco unit is reading the resistance of the other ranco unit.

Is there something I can put in series in the wiring that will make this work? I was thinking a shunt of some kind between the splice and and the positive side of the controller might do it.

 

The probe acts similar to a variable resistor in a circuit with a bias voltage applied to it, so wiring a single probe to two circuits will just confuse both. And removing the power from one of the units while leaving the probe connected to both just introduces a set of out-of-scope circuitry to load the powered unit.

I can't think of anything you could do to make this work...

Cheers!