Ford Fiesta heater won't warm up - how can I fix it?

The blower is working on my Ford Fiesta, but it's not warming up. Any idea what the fault could be?

Asked on 3 January 2020 by steve

Answered by Honest John
Likely that either the valve between the engine coolant pipes and the heater matrix has failed or that sludge in the bottom of the heater matrix is impeding the flow of coolant. One Fiesta owner recently reported that the shock of speed humps and potholes dislodged this and the heater started working. Might work to give the system a flush and reverse flush with Radflush from a car accessory shop.
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