Heater valve stripdown & fault investigation
Video shows the stripdown and investigation as to why the Fiesta/Ka/Puma heater valve failed. As you can see in the video, coolant somehow managed to get past the various seals and into the field coil (solenoid) thus causing no movement of the plunger valve. Some heater valves fail in fully closed or fully open position. Off camera I ran 12 volts to the coil using a Sealey Test Probe and it moved the steel plunger rod but not by enough or with enough force to move the actual plunger valve where it sits within the body of the valve. I'm guessing water has affected the coil.
I was going to repair and reuse it but since my new unit turned up today (6th Jan) and I only ordered it on the 5th from 'directsupplies1' on Ebay.co.uk, (thanks guys!) I might as well fit a new unit since any repair to the old valve might be short-lived. Even though I advocate repairing instead of throwing away there are times when it's safer, cheaper and simpler to fit new components. Since this is a common car parts are available. If it was a rare classic then often repair is the only course of action.