Chiller not staying at set temp?

[kiwi axolotls]

i recently just brought a chiller for my tank, Hailea hc150. Ive set the chiller to 19 which is what my tank is constantly in the winter and obviously don’t want the temp changing around too much.

It’s been set to 19 but my tank is 20 and it automatically turns off. the water is still going through the chiller but the tank temp ever so slightly creeps up and the chiller temp doesn’t change. i thought maybe once it started going past the set temp it would kick in when it started going up again but that’s yet to happen and i have to keep restarting it?

the instructions don’t really explain well

 

[wolfen]

axolotls do best at lower temperatures 15°c - 18°c being ideal, unless you are keeping your axolotl in breeding condition it would be better to set the chiller to around 15°c, this will allow for any temperature creeping up without stressing your axolotl.
the temperature sensor in the unit might not be picking up on the increase in the aquarium you may have to use the temperature error adjustment which is described in the manual.