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I'm guessing this headache came up at once. ... The problem is the hob is only getting half of the power it needs to operate. I would look to where the hob ties into the main power supply. My guess is that corrosion has formed and you lost contact. Now just so you know sometimes it doesn't take much to break connection with electricity. Please remember to turn off the power before you attempt to do this. Also look to where the current ties into the hob it's self. This isn't uncommon as well and the same can go at the fuse/panel box. Double check all those connections. If you have any other questions, please ask. If any of these don't cure your problem, please come back and we can go from there. I wish you the best.