I'M KNEW TO THIS FORUM (AND TRACTORS IN GENERAL). MY DAD JUST PURCHASED A USED L3600. THE PIGTAIL LOOKING(MAYBE GLOWPLUG) WARNING LIGHT HAS COME ON TWICE, BUT GOES OUT AFTER A MINUTE OR SO. WHAT SHOULD WE LOOK FOR. THANKS IN ADVANCE!!
Are you seeing the glowplug light come one while the engine is running or when you are starting the engine? If the weather and engine are cool enough, I think this is normal on startup, but should not happen after the engine is running. It might indicate a worn glowplug, defective relay or control board, or wiring.
If you mean the light comes on sometimes while running take a look at this thread. I was the op on this thread and I have a late 1990s L3600. Hope this helps.