Help please, my focus is a 2012 with climate control. I can either have very hot air or very cold and nothing in between. Doesn’t matter if using just heater, air con or climate. I’ve changed the cabin temperature sensor. 
 

what’s next? I’ve seen on YouTube someone saying the control panel can cause this?

 

any help greatly appreciated 

 

tony

You might expect the dial to be an electrical component, but I've seen a video before that showed a heating control panel dial that moved a wire, similar to how on a bicycle you might pull a lever which pulls a wire, actuating something at the other end. In this video the wire had somehow become disconnected from the dial. So you might find that you have the same issue if you disassemble the front panel to look behind the dials.

Also, note that the coolant from the engine is circulated through a radiator-like component called the 'heater matrix', located behind the dashboard. This is done to provide free heat from the engine. Some models may have an additional heating element that gets used when there's not enough heat from the engine, for instance upon cold-start. The engine cooling system has a coolant temperature sensor. Perhaps this sensor could be faulty and confusing the control system?