i have a 250w Jager heater i just bought 2 weeks ago. i noticed last night that the temp in the tank was 90. my heater was set to 79. i floated an ice pack for an hour and a half to get the temp back down. all day today i had it set at 79 and no problems i had the door open and it was 11 outside. tonight it's climbing again. the heater light is still on and producing heat even though it's set at 71. temp in the tank is 85. is this a malfunction or what. anyone help me in this situation as to what is the problem?