I don't think your thermometer is meant to be submerged where the probe hits the wire lead.
I did that with mine, and it read 189F after a few minutes, even ice cold water only dropped it 2 degrees.
I let it dry out for about 5 days, and it works again.
it's a digital oven thermometer, so I gotta be careful about letting it fall all the way into the brewpot.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10