I have a 2013 4.4 SDV8. The FBH has never worked but I have had heat from the vents when I have needed it. Recently I have not been able to get any heat from the front or rear vents no matter what I do. Coolant level is OK and engine temps are fine.

I have checked for error codes and only have;
B12A6 Auxiliary heater water pump
B13C2 Windshield misting sensor

The B12A6 would make sense why the FBH isn't working but would that affect the normal heating via the engine coolant circuit?

It has been suggested that it might be the FBH diverter valve that is stuck?

Anyone have experience of these issues?

I ordered a new water pump for the auxiliary heater and a new diverter valve. I have just replaced them both and now have hot air coming through the interior vents at last.

I'm not sure which part did the trick but guess as others suggest it was the diverter valve. Now the colder nights are coming in I will be able to test the auxiliary heater with the new pump.

Will update later.....

hi i have same problem, no hot air coming can you please let me know were is located the ( diverter valve) thanks

Hi,

It is mounted directly under the auxiliary heater. This is located on the drivers side between the brake fluid reservoir and suspension mount. You will need to remove the Road wheel and wheel arch lining to disconnect the aux heater exhaust first. Then a few bolts and a couple of hoses will release the heater so you can get to it. To be honest it’s not a difficult job but access is tight and you need a bit of patience!

Good luck