I'm having issues with my auto temp controls. I can set my temp at 74 degrees and adjust it hotter but it won't stay warm/hot unless you lock the **** past 82. Then it turns to a furnace. Tried changing the controller but no change. Any ideas would be helpful. Thanks.

 

Welcome to the forum...
Just a thought but has the heater core been flushed? maybe in consistent flow is an issue...