Marentette,
I'm aware of the problem and that there is a fix or a workaround. But we do not get very cold here in California and it has been a while since we have had to deal with this. I can't remember what the fix was, partly because early on there were several different "fixes". One involved restricting the bypass with a small ball valve that you closed down in winter. But I think they may have come up with a more "factory" solution after they tested that.
The thermostat controls engine temp, and in theory stays closed until it reaches a set number, let's guess that is 180 degrees. Unless you are in extreme weather (think well below zero), the engine should run no colder than the thermostat designation. But like most vehicles, there is a bypass that allows some coolant to go around the thermostat. On these engines, the bypass is big enough and the radiator big enough that the small amount bypassing cools the engine down below 180. On a normal day working the tractor like pulling a disc or mowing with a decent size mower, it will get to temp. But a cold day with a light duty job means it over cools and never warms up. While it is better than overheating, it really is best for a diesel to get up to temp and not run around cold.
I am sure the dealers and the service reps in the cold country have a solution. Any other dealers chime in?
If you totally strike out, I can contact MUSA and try to get the approved fix....if there is an official one.
I have seen machines before that needed no fan. If it was as easy as removing the fan and everything was fine, would that not be an easy fix and it would give you more power. A lot of semi trucks block the radiators all the time in the winter.