Had an issue with the heater controls since putting it back on the road in October. If you turn up the drivers side, it stays cold and then randomly it will go hot a while later and you can't seem to turn down the passenger side from hot to cold. You can turn the knobs but the temp doesn't change. 2004 RR 4.4 V8 Autobiography

Does it work if you put it on full hot or full cold?

there are 2 valves which control the flow to the 2 sides of the heater matrix, from memory i think they are located on the passenger side front wing. maybe they are duff or a tap would free them up.

alternatively i would check that the thermistor in the dash isn't covered in dust, get an air blower and blow out the little vented area near the knobs. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
KIA E-Niro 4+
2021 Discovery 5 D300 MHEV commercial

Hi, if you put drivers side up on full hot it stays cold then it might randomly go hot. Passenger side never turns down from hot whatever you do. The vent by the knobs is covered in dust actually as I haven't had chance to clean it out since being back on the road. The vent flaps in the wings is also sounding like a possibility, didn't even know about those either. Does anybody have any pictures of the vent flaps so i know what to look for? 2004 RR 4.4 V8 Autobiography

Cleaning the dash sensor hole is the easiest thing to try, and quite likely. AIUI the temp controls are relative temp really, not an absolute temp. The sides can only be (I think) 6 degrees apart, so you can't have one on full hot and one on full cold. In the user manual!