SWMBO's heater isn't working. Car is a '99 (Mk 5?) facelifted Fiesta 1.25 Ghia. Googling more-or-less confirms the obvious - it's either the sender control on the dashboard, or the valve in the scuttle (fuse 13 is OK). If I measure (a) voltage across the cable and (b) resistance across the valve, what should I expect to see?
Maybe clutching at straws, but the car was recently serviced and I'm pretty sure the garage changed the coolant. Could it just be an airlock in the heater loop? If so how can we clear it?