Temp gauge problems.

Have you verified that your car isn't just running cold? A thermostat stuck open or a missing thermostat could cause a low reading.
I thought about that too and and even if the car was just running cold the gauge sits below the cold mark and stays there no matter how much I push the car or or let it sit. The thermostat being stuck is another possibility I guess but it worked fine a few weeks earlier and I don't know why it would just up and quit working. How would I go about testing any of it?