Sorry for borrowing your post but...
I did a M-tdi (AHU) conversion in my old Mazda truck this weekend. I had a 1.9 AAZ in it before. And I had to hook up the glow plug coolant heater system to get some heat out of it.
I hooked them up to a relay so that whenever the alternator is putting out power the glowplug heater is active. That way I donīt have to worry about overheating the system or draining the battery.
Mine starts without problems without blockheater or working glowplugs in -14 Celcius (checked it this morning). And the engine has 420000 km on it
I couldnīt beleive it myself.
I should have gone with a M-Tdi a loong time ago if I knew this earlier.