I'm waiting on the repair manual from eBay. This is a new to me unit, overall it seems to be in decent shape and luckily all the grease fittings except a couple took grease. The first & main thing I want to repair in the dash / warning light area display. The one in this unit has every light on and they have been on so long they have ruined the plastic cover. I'm wondering if this display malfunction is common? I ran over a chunk of rebar and ruined a tire, the same size new tire is shorter and skinnier, so this week it will get 3 more new tires to match. Even though the tire says it is the same size, they are not even close. This is my third JD grader, I always sold the others once I finished using them for whatever project we had going.
I believe the key switch G terminal is grounded when the key switch is in the start or monitor bulb check positions only. Check if it is grounded in the on position.
Follow Dave's solid advice. I ran a new 770BH decades ago. Good reliable machines. Tire size is aggravating. Very few brands will interchange.
Thanks for the advice, I will replace the ignition switch. They have it rigged now with a toggle switch for the on / off.
Report back with the results.
Be sure to get connector ( item #3) in screenshot below as well.