What warning light is that?

Well for instance, all these come on when I first start my car. When I use my heater fan the battery, the dummy light fir overheating, the gas, the headlights and brakes all light up. They go dim when I turn my heater fan off. But the battery light stays on. Would it be something to do with my battery. It's showing on the gauge that it's got a good charge. It's really got me confused, just started doing this. Thanks for responding back to my comment.

This indicates a likely charging fault. It could be a faulty ignition switch, blown fuse or a faulty alternator.

What voltage is the voltmeter showing?