I've had the same problem before and after a new thermostat, but have never had a problem with over heating. I have a feeling the gauge is very sensitive.
Check into the temperature control valve--this is different than the thermostat.
The heater cor was replaced but it is still not getting warm
If a thermostat is not working properly, you cannot calibrate it. It must be replaced.
Thermostat probably needs to be replaced.
Was the gasket replaced? Have you checked the hose and the heater core. Is everything tightened down?
heater core plugged or air locked check to see if hoses going to heater core are hot
MY CAR WAS DOING THE SAME THING NO HOT AIR COMING OUT OF THE HEATER I CHANGED THE THERMOSTAT. IT WASNT THE THERMOSTAT. I GOT TO CHECKING AND THE SEAL IN THE WATER PUMP WAS BAD. I REPLACED THE WATER PUMP AND IT WORKS FINE NOW.
Try flushing heater core Try flushing heater core
How did you change the thermostat?
The heater valve could be failing to open for one reason or another.
usually it is a vacuumn problem right at the heater control switch or sometime under the hood
Yes it can be replaced, if it is of the replaceable type. If you are in doubt about how to do it, perhaps you should have it done by a plumbing professional.