I haven't got a lcr so you can ignore me! In my fiesta zetec s I had the same
problem, I'll only get heat if I put my foot down on the dual carriage way. I found it wasthe heater control valve, I changed this and boomy heating is toastie.
You could have a similer
problem with yours, you could locate it and disconnect it and put a live feed to it to see if it opens and closes. If it does then you know it's a
problem elsewhere. Hopefully what I said shines some light.