Based on your description, the thermostat or temperature gauge are suspect before the direct-coupled fan.
Thermostat should remain closed until nearing operating temperature, disallowing any real cooling effect, regardless of what the fan is doing. With no coolant flowing thru the radiator, the fan has little effect on engine temp.
Easy to test tstat in a pan of heated water with a thermometer on the stove.
BTW, what temp. tstat is installed?
Additionally, the temperature gauge may be lying to you. Easy to test with an IR thermometer aimed near the tstat sensor.
But remember, these IDI diesel engines don't generate much heat unless under load. IOW, simply idling in cold weather may not bring the engine up to operating temp. for a long time.
What is your testing method?
Check recent posts, someone with a similar situation (either a Pinz? or VW LT?) suffered months with their perceived temperature problems before discovering it was a faulty temp gauge.
