When I plug mine in, I can hear a soft electrical "snapping" sound when the contact is made. It's a quiet enough sound that I only hear it if there is no traffic on our street. It is about 400 watts, so imagine the sound of plugging in a 400 watt light bulb while it's turned on. I agree it would be nice to see the actual voltage at the block heater's AC input, as well as the current draw. I know I have 122 volts AC at my breaker box, but after 100' of 16/3 wire, who knows? Especially with all the salt and grime on the plug.

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic