Sounds like the heater has a short with enough leakage current to trip
the GFCI and needs to be replaced. You could also try running an
extension cord to another GFCI circuit and see what happens, but I
would expect it's going to trip too.
Next step is replace the block heater cable (from underneath the car). It's
a $5 mail order part or $50 at the dealer or something like that. That SHOULD
fix it as the cords to seem to short out with age - they harden and crack then
a bit of water gets in there.
Oh yeah. BTDT. I have like 3 spares of that part now. Just in case.
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
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