So, my Fiesta only blows cold air through the blowers no matter what the settings.

I checked the temperature of the inlet hose to the heater valve and it was warm, and cold on the other side. This suggested to me that the heater valve was busted (common problem) so I replaced it easily and cheaply enough.

It still blows cold air on all settings, however. I felt the hoses again and they are still warm on the engine side and cold the other side of the valve.

I guessed that I might have been unlucky and got a bad valve however I connected it up without the hoses connected and watched the valve move in and out as I turned the heater dial in the cabin.

I thought maybe the matrix is choked up so I flushed this through with the garden hose. Not only did nothing really much come out of it, but the flow was quite quick and it certainly didn't seem restrictive.

My problem is that something is forcing the warm coolant down the bypass in the heater valve even with the valve open, but I can't figure out what!!!

Any ideas please?