Correction to what I said above, the timer that he points to under the hood is for the Glow Plug Indicator Lamp and not the glow plugs, For the other TC tractors, I believe it controls both the indicator lamp and a relay that energizes the glow plugs. I suspect the TC30 is similar to the xx20 series where the glow plugs are engerized direct from the ignition key 'heat' position and timer only controls the glow plug indicator light