Heater Staying On!!

I've had my setup for almost a year now but for the last 4 months I've had to start over. Been cycling, now have plants and a sucker fish, water is always 78. Yesterday afternoon I did a 25% water change as usual but also cleaned the filter which took a little longer than usual. Plugged everything back. Late last night I noticed my water was at 92!! I unplugged the heater but left it in the tank. It's a regular one dial heater with Low and High. Now that it's at 79 today on its own, I put the heater dial to the lowest notch and plugged it in (planning on upping it until the light turns on and then back one) but the light comes on right away, on the lowest temp??? Any thoughts?

 

What is the temperature in your house? It's summer, so if you house is reaching those temperatures during the day when you're not home, your water will too. Otherwise, time for a new heater.

 

My house has central ac so it's definitely not hot inside. I just don't get why the heater is turning on on the lowest setting if the water is at 79. I'm asking cause maybe there's a step I don't know about after unplugging it for an hour or so which I've never done before..?

 

It may be time to replace the heater but until you do have you worked the knob all the way up and them all the way back down? If not, do it several times. Occasionally knobs that are left at the same setting for long periods of time get kinda corroded (well not exactly corroded but just needs to be used) Just unplug it and work that knob back and forth several times and see if it helps.