What does it usually mean if your temperature gauge suddenly doesn't seem to register a temp? Normally, the needle stays around the half mark, today it begins to raise a little and then goes back to nothing.
When you don't see the temperature gauge go up, it usually means that your thermostat is stuck open. You will probably notice that it takes a long time to get heat in the vehicle as well.
It may be that it was just stuck. If it continues to do this however, you'll need to have the thermostat looked at and replaced.
You can also check the coolant level by looking at the reservoir bottle under the hood. If you need to add coolant make sure you check the manufacturers recommendations and that it's a 50/50 mix of antifreeze and water. It should be to the "fill" mark on the bottle.
〉 Answered on Feb 17th, 2008 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines