Output goes to 0 when above setpoint.

[ZachElkins]

I am running in to an issue where the output is always 0 when the input is greater than the set-point, but seems to be working fine when it is below it.

I think at least one other person is having the same issue, found in the Google Group. (https://groups.google.com/g/diy-pid-control/c/Z9zokl6ngZQ)

[heaterC]

As you can find in the documentation, the output window is by default 0-255, but you can easily change this.

[drf5n]

Yes, the default output range is set to the analogWrite(...) range of 0-255. If you want it to go negative, use SetOutputLimits:

https://playground.arduino.cc/Code/PIDLibrarySetOutputLimits/