My Honeywll Chronotherm III thermostat does not maintain the hold temp.
It is my understanding that the hold feature should override all programing yet sometimes I press hold and warmer button and it will flash and default to 62 degrees it may come on and run heat for a few minutes and then click off.
Last night it came on and ran the heat to 70 degrees.
It acts as if the hold feature is not working all the time.
Right now it is functioning properly and holding at 64 degrees.
The batteries are fresh.
Any ideas??

The Chronotherm III is an old stat. I would suggest replacement.