I have a 3 zone system. The thermostat which is hooked up to where my master one used to be is able to use aux heat when I need it to. The other two are unable to use aux heat and only use the heat pump. The main thermostat did have an extra wire going to the control board on my air handler. The other 2 did not have this. But the old thermostats had no problem using aux heat. Any fixes for this?
