I have a 1999 with v6 3.0. When the car sits after running for 30 minutes the temp gauge is normal but there is little heat. When I drive the car the air is hotter. The temp gauge doesn't change. What could be the issue?

 

There is a good possibility the water pump is starting to fail. If you sit still in park and raise the rpm's, does the heat increase? If it does, I would look at the water pump. These were bad about wearing the impellers off and not circulating the coolant.