Heater Won't Shut Off

[Mako Man111]

Ok, I got a new 100 watt heater(fully submersable) for my 20 gallon tank and I set it to 75 degrees, and I just got back home after a hockey game and its still on and the temperature was just about 81 degrees, thank God I got home in time to unplug it. What could be wrong??

 

[sparrow6190]

it seems to be calibrated wrong, in need of repair.

if you can take it back to the store and get another one I would.

 

[afireinside]

I have a heater when I have to turn it on and off manually. It sucks, but I can get it at an ideal tempature. This is in my 10g btw.

 

[Fadi]

I had this problem with one of my ALL GLASS AQUARIUM Heaters. Good thing I have discus in that tank.