ironhorse wrote:

pull the fuse out that controles the fans (cant remember the number) its one of the big ones in the glove box

run the FBH for 20 mins then either test the water temp and/ or replace the fuse and feel the warmth comming out the vents (very toasty)

This morning I ran the test (outside temp 3 degrees C)

1) Remove Fuse F64 (50 amp, disabling the interior fan to front/side windows)
2) Activate heater
3) Insert fuse after ~ 15 minutes

Unfortunately, same result as always, warm(ish) air, but for sure not hot nor (very) warm.

I'm afraid this is not the cause (nor solution) of the issue.....  Range Rover Vogue, MY '06 TD6 3.0 Tonga Green

i would say you have a changeover valve problem because mine makes a great deal of differance when i delay the fans operating
the temp gauge is also well off the blue before start up when tested this way

Thanks ironhorse, then I definitely need the change over valve (the famous number 24 on the drawings)

Wondering if this can be bought at at reasonable price somewhere and even more wonder if the wiring is then already there to connect it....anybody happen to know this and the partnumber?

Also, the FBH is producing "x" amount of heat. Without the change over valve, I think it means that the FBH is using this to heat both circuits (whereas the thermostat is closed). So as the "total amount of heating" is not changing, it means that if the interior would be "toasty" (forget about the fans for the moment), then the engine would actually be colder?

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Workshop manual:
"The changeover valve isolates the heater coolant circuit from the engine coolant circuit"

Changeover Valve
"The changeover valve is a normally open solenoid valve installed between the supply and return sides of the heater coolant circuit. The changeover valve is located in the engine compartment on the engine bulkhead. When deenergised, the changeover valve connects the heater coolant circuit to the engine coolant circuit. When energised, the changeover valve isolates the heater coolant circuit from the engine coolant circuit. The changeover valve is controlled by a power feed from the ATC ECU."

On receipt of the messages:
- A red LED on the MID/MFD panel flashes at 2 Hz to indicate that parked heating is active.
- If the ambient temperature is less than 5 °C (41 °F), the BCU activates the door mirror heaters for 3 minutes

The ATC ECU
- Energises the changeover valve
- Sends a K bus message to activate the FBH
- Operates the blower at speed 1
- Opens the windscreen distribution flaps in the heater assembly and closes the face and footwell flaps.

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My outside mirrors by the way for sure are not heated for 3 minutes below 5 degrees C outside temperature, but that probably is another problem not related to the current dicussion  Range Rover Vogue, MY '06 TD6 3.0 Tonga Green

So, is my understanding correct that when the Change Over Valve is fitted, only the interior will become warm? (And probably much more warm than now, as the amount of cooling fluid will be less?)

I would find that strange. It means that when start driving, the cold fluid would be mixed with the warm fluid???

 Range Rover Vogue, MY '06 TD6 3.0 Tonga Green