Ford Flex seat heater failure

Sounds like a common issue. Have you checked the thermal sensor? Sometimes that can cause the heating element to shut down prematurely. Do you have access to a multimeter to check the resistance of the heating element itself? Also, which seat is affected?

I haven't checked the thermal sensor specifically. It's the driver's seat. Where is the thermal sensor located, and what resistance range should I be looking for?

The thermal sensor is usually integrated into the heating mat itself, so you'll need to access the seat heater element. As for the resistance range, that information can be tricky to find without specific Ford documentation. Given the error code and that it's not heating at all, and you suspect the mat, it might be best to get it checked by a workshop. A defective seat heating mat sounds like the most likely culprit, and it's a fairly involved repair.

Thanks for the advice. Took it to the shop; confirmed defective seat heating mat. Repair cost 390€.