I believe that is the same series and vintage as my L3010. When you click from off to on the glow plugs come on. There is a temperature controlled timer that determines how long they are on. When the glow plug light goes out start the tractor. 10 seconds seems normal for cool but not frigid temperatures.
Does it start right up like it should - that will tell you a lot.
This is not published but if you need more glow plug time you can manually control it by putting the steering column shift in forward then turn the key to start. It won't crank and the glow plugs will come on. The glow plug light will NOT come on. Hold the switch on start for as long as you want the glow plugs on then put the shift in neutral and it will turn the glow pulls off, crank, and start.
gg