with key in off position the gas and temp gauge start moving up and down with a buzzing sound

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My 2000 Cabrio wouldn't start so I charged the battery using 10 amps for a few hours. Car still wouldn't start and when I put the key back in the off position the gas and temp gauges started going back and forth like windshield wipers and there was a loud buzzing sound. Also the rpm gauge went to about 10k rpms. I had to disconnect the battery to get it all to stop?? Any ideas you might have will help me a lot Thank you very much, Don Smith

How long has your 2000 Volkswagen Cabrio had this problem?

Always there now