</font><font color="blue" class="small">( I actually read my 1720 manual the other day, & it said the glow plug lamp on the dash will go out in 4 seconds (more like 7 actually) but that if it is really cold, below x degrees, you should hold the key in the gp position for an additional 4 seconds after the light goes out. This tells me the lamp is on a time circut, the glow plug actually isn't. Don't know how that relates to other NH models.
--->Paul )</font>
I dug out my 2120 manual and it's basically the same as above. It states that "Important: In cold weather below 23F (-5C) start the engine after holding the key switch to the "HEAT" position for approximately 10 seconds even if the glow plus indicator warning light has gone out."
This is not something I knew about my tractor, I usually just did the 4 second thing 2 or 3 times. It also stated to make sure the tractor is in neutral.
Andy