How to Recalibrate old Eheim heater

[Kareen]

I have the old Eheim heater w/ the button on top how do you Recalibrate them Iv had one in my tank set at 82 now I need to set it at 75and I can't remember how to do it.

 

[Starm]

I was having the same issues with my old ones, they would heat many degrees over what I set it at.

 

[stany]

I have one I've been struggling with that I can't seem to get below 84 without not working at all. I just spent the $30 and replaced it. .