Before winter really hit I got the electric cabin heater working, or at least I think I did. When I flip the switch I can hear the relays click, and the fuel consumption goes up by ~0.1-0.15 liters per hour. I also checked the heating element itself - when taken out of the airflow it goes from 0 to 25°C after a few seconds, so it works. On the other hand, I can't feel any difference when I place my hand over the ventilation vents. Neither does the IR thermometer see a difference. After some thought I decided that a 400W or 600W heater doesn't really give that much heat, especially when the fan is blowing LOTS of freezing air over it. It's not like a 2000W heater warming up room-temperature air. So, I've used the heater a few times, but I still can't be sure it really helps warm up the cabin.
On a different note, I got to park in a heated (+5°C) garage for a week and used that chance to do a few things. One of them was to hook up my ScanGauge in a semi-permanent way:
It is now closer to my line of sight (compared to sitting in the ashtray or on the steering wheel column), so it is easier to focus on while still paying attention to the road. Also, the cable is now hidden inside the dashboard, I had to make a hole in the dash to make everything nice and purdy
In fact, it is not the original cable, instead I cut an old ethernet cable and wired it the backside of the OBD socket, so the socket is now free to be used.
A big thanks to AndrzejM for help with the SG
I also added some insulation around the engine. The air filter box hangs on the rear side of the block, gaining lots of heat from it, so I glued some aluminium foil to it to reflect some heat. This should lower intake air temps, and help the engine keep its heat when parked or using the preheater. For the same reason I inserted a piece of bubblewrap (with alu foil on one side) to shield the intake ducts and battery from the engine and coolant lines. It's not much, but hopefully it's worth something.