My Bobcat 553 interlock just started acting up a couple of days ago. I noticed that it would only "lock up" when it wasn't at idle. Today I was watching the voltage meter on the panel and saw the voltage creeping up from ~14V to eventually maxed out ~18V. When the voltmeter creeps into the range above 16V or so the interlock lights all flash and everything locks up. I've gone through the forum threads here and removed/cleaned the seat sensor, safety bar switch, park brake switch, and even removed/cleaned the interlock solenoid. Everything seems to be functioning as it should: when you start up the lights for the various safety devices light up as they should (the seat, safety bar, parking brake..). At first everything seems fine - then, once you raise it above idle, the voltage begins to slowly creep up and it locks up. But it doesn't just "lock up" - the interlock cycles on-off-on every few seconds. Again you can watch the voltmeter and the "off" state (unlocked) corresponds with the voltage dropping down to 14-15V range. Or you could say the ON or LOCKED state corresponds with the voltage spiking to 18V. Has anyone seen this? Am I on the right track? Do I need a new alternator/voltage regulator or a new battery or both? Any help would be very much appreciated.