Please make sure everything is powered down and switch off before you start to group two heaters together.
When you want to use the Pro controller with more than one heater, here is how you can correct these up.
Plug your pro controller into your 1st heater wiring loom via the 4-pin connector as shown below in Pic 1.
in regards to the 2nd heater, you need to join the CAN-BUS wires from the loom in Pic. 2 to the loom in Pic. 1 you must join up the (blue/red & Blue/black) to both looms.
Once these wires from both looms have been corrected, once you power up the Pro Controller, it will now ask you to re-group and should now detect both heater systems as heater 1 & heater 2.
1st Heater wiring loom (Pic1)
2nd heater wiring loom (Pic 2)
