My guess is mice may have 'visited' your instrument panel. They may have chewed wires and caused a short. Also, your relays and fuses are down there too. Your instrument panel doesn't come out like larger models. On them you just remove a couple of screws and the whole thing lifts out. On your tractor, you'll have to remove the cowlings on either side under the steering wheel to see up under your dash panel and inspect the area for evidence of mice or burned wires or components. Here is an illustration of your dash panel components. I'm not sure, but I believe items #1, #2, & #4 will have to be removed so you can look up under the instrument panel.
It's not really a schematic, but an illustrated parts diagram (just splitting hairs). New Holland has these online for free. In this case it is one of the TBN sponsor dealers, Messicks. Go to this link and enter your tractor model in the block (TC18). You'll be presented with a list of options below the box for different tractors. Click on the first one in the list and it will take you to a screen of frequently used parts. Close that overlay and the background page is the illustrated parts by system. Click on the system on the left side and you'll be presented with an illustration and a list of parts. It's great for showing how things go together.
Thanks to jinmam I was able to print a schematic and know what to expect....was hoping to find a burnt wire but, found a melted regulator instead...its on order now, will let you know if it works!...thanks again!...