Thermostat Stuck Open

Is it bad if the Thermostat is stuck open?
I have 99 Ford Explorer as I have noted in a previous post that runs cool and it has been suggested to me that my Thermostat may be stuck open. Is that bad for the vehicle.
I get great heat quickly and have not noticed any change in gas mileage, but my temperature needle only slightly rises above the "C" in my gauge.

If the upper radiator hose is HOT to the touch, it's not really running cool.

Is it bad if the Thermostat is stuck open?
I have 99 Ford Explorer as I have noted in a previous post that runs cool and it has been suggested to me that my Thermostat may be stuck open. Is that bad for the vehicle.
I get great heat quickly and have not noticed any change in gas mileage, but my temperature needle only slightly rises above the "C" in my gauge.
yes a t-stat stuck open is not good.it will cause longer warm up times,increasing wear during cold starts.although those temp gauges arnt the most accurate.if your in doubt you might as well replace it,since its easy to do and very cheap.