Temperature creep in incubator

[MysteriaSdrassa]

Just recently aquired a used Little Giant styrofoam incubator with a wafer type thermo on it from my recently deceased grandmother. (She is the one who originally got me interested in chickens years back with a flock of Black Minorcas,, still my all time favorite bird) Anyway,, I decided to test it out on a small batch of eggs and noticed that it held a nice steady temp kicking on and off like it should up until the start of the 3rd week at which point the temp began to creep upward so that I had to constantly keep backing it off to hold a lower temp. I had a nice hatch (about 95%) due to good vigilance. So I decide to give it another try,,,, same thing,,, it holds a nice steady temp up until the start of the third week and them up it started to creep again.
Is this normal for a wafer style thermostat or is there something screwy with this one? I've only used digital types before and my home made incubator uses digital, but thought it would be kinda nifty doing it with something my grandmother used

 

[AmyLynn2374]

Just recently aquired a used Little Giant styrofoam incubator with a wafer type thermo on it from my recently deceased grandmother. (She is the one who originally got me interested in chickens years back with a flock of Black Minorcas,, still my all time favorite bird) Anyway,, I decided to test it out on a small batch of eggs and noticed that it held a nice steady temp kicking on and off like it should up until the start of the 3rd week at which point the temp began to creep upward so that I had to constantly keep backing it off to hold a lower temp. I had a nice hatch (about 95%) due to good vigilance. So I decide to give it another try,,,, same thing,,, it holds a nice steady temp up until the start of the third week and them up it started to creep again.
Is this normal for a wafer style thermostat or is there something screwy with this one? I've only used digital types before and my home made incubator uses digital, but thought it would be kinda nifty doing it with something my grandmother used

I have to adjust mine down too. I think the biggest reason for this is as the chicks get bigger, they start to give off their own body heat and if you are not using an incubator with a thermostat control for the heat, you have to adjust it down. I use the 9200, most likely the one you are using and have the fan kit installed.

 

[AmyLynn2374]

And sorry to hear about your grandma passing.

On a better note:

 

[MysteriaSdrassa]

Thanx

 

[AmyLynn2374]

You're welcome.