Having problems with the heaters in my xr3i. They put out good hot air within a few minutes usually but all of a sudden have stopped getting hot.

Driving for about 12 miles today and they suddenly went hot then cold again! Don't think its the matrix as they are usually really warm.

I think its the thermostat alothough thats only a year old. Also noticed fans are on when engine isnt really that hot.

Am i right in thinking its the thermostat???