Glow plug light quit working

I have a 2002 Grand L 3010 ( I can't believe that tractor is now 11 years old, my how time flies). Narry a problem with the tractor till now. The glow plug light no longer comes on when I turn the key. I can start the tractor but it takes a few turns of the key if it is low 60's. If it is above 70 it will start anyway. But I know before fall I'm going to have to get this issue figured out, but I don't know where to start. Never had this issue before.
Any ideas?

Is it the light only or do the glow plugs themselves not warm?

Guessing the glow plugs don't warm as it is harder than normal to start.

I'm going to guess it's either the switch or the relay. When you turn the key to the glow position, do you get an audible click from the relay?

nope, no click.
Where would the relay be and what would it look like?

Doc,
I consulted a friend who knows this model. He said there is a timer, controller, and relay in top right of dashboard. They are parts 010, 020 and 030. One of them may be bad. Now which part is which, I don't know. But here is a scan for you.

Thanks Jerry!!!!!!!