I have about the same thing happening to mine. The light on the dash does not come on, but the glow plugs still work and the car still starts right up. I'm guessing from previous posts, that it may have a certain plug out that causes the light to not work. I replaced the g.p.'s not long ago, but I understand that its not uncommon for them (or any electrical component for that matter) to randomly quit working no matter the age.

I went through 3 starters (the third one being the "charm") before I got my car to crank over correctly, and it turned out that the first two, although new (rebuilt), were just not working. And if anyone has changed the starter in a 617, you know that its not the easiest job...its not hard, but its tedious. I finally figured out if I turn the wheel all the way to the right (or left?) I had an easier time getting the starter out of the engine bay through the bottom.

Anyway, yea...sometimes things don't work although they're new...