usually when I do water changes the red light turns back on when im done and plug it all back in. even if its above the temp I have it set for the light is on indicating heating but never for long then it goes off. when I plugged it all back in the light never lit up. My tank thermometer is reading 83.5 and I have it for 78 I believe. maybe was 80. was 78 or 80 I forget and its hard to read. but the temperature is ok Im just worried because when I didn't see the light I wondered if something could be wrong with it?