Furnace doesn't turn off

[RicoRed]

We have a 2018 Landmark 365 Madison and the furnace didn't turn off while we were out. Thank goodness we have a Marcel in our unit and it alerted us that the interior temp hit 85 degrees. We also have 3 dogs! Fortunately we were only a half hour away. Any ideas as to what happened? Bare with us, we're new to this forum. Thanks in advance

 

[wdk450]

First thought would be a thernostat problem. If it is overheating, and you lower the desired heating 20 degrees or more, what does the system do?
Remember that the furnace normally keeps running for a couple of minutes after a hot enough temperature is sensed.

 

[MirageFlare]

Wow, that’s a close call thank goodness for the Marcel and that you were nearby! It sounds like there could be an issue with the thermostat or the furnace relay getting stuck- check if the thermostat is calibrated properly or if there’s a wiring issue.