So my 320d has been in my possession for 2 years now, and it has always had a "40A1 alternator load signal" fault and a "B+ short circuit to ground" on the electric heater in the DDE5.0. Needless to say, the heater did not work.

I decided to try and fix these issues 2 days ago, so I swapped the voltage regulator on the alternator, cleaned the sliprings as nicely as I could, and installed a second hand aux heater from Lithuania, a HW version C 03 (which should be the newest).

Now I've been driving it around for the last two days with ambient temperatures around -1 C, toggling the IHKA on and off, up to 32 C on full whack etc, but I don't see any change in the revs on the tachometre and no change in charging voltage from the alternator. It stays at 14.2v very consistently. I checked the DDE for errors a number of times and the two faults have not returned. I have also forced the heater to work through INPA's "Activate" page and it seems to work when I do so - the engine tone changes noticeably, though the revs still don't jump up visibly. After this, there are still no errors in INPA. Battery voltage is at 12.4v when engine not running - should be almost full?

So the questions: why is the heater not turning on on its own when I turn up the heat, only when forced through INPA? Is there a reset process to make the car use it after it has been switched? Anything else I could try?