Cold start aid button on ford 1910

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The heating element that you see on the dash is wired inline to the glowplugs mounted in the engine cylinder head.
I have two questions for you..... .
1) does your tractor still crank normally?
if yes....you have a burned out indicator
2) if it doesn't crank normally you may still have a burned out indicator, or. you may not
be getting power to the circut when you hold the key to preheat.

You need to take a test light and test for power on the terminals of the indicator with the key held to the preheat detent, if you get power in and out and the tractor cranks ok, then I would say the element is bad,
if you have no power into the unit, then your trouble is in the power wire to the element from the switch

good luck

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The glowplug circuit really has nothing to do with the cranking circuit. Test for voltage at the glowplugs with the key in the heat position. If your 1910 will start at all, you must be getting some heat from the glowplugs, cause they will not cold start without it. As long as there is enough current to make the plugs hot, there is little cause for worry.