Hello I have a 2001 cavalier with a 2.2 litre engine. When you start driving the car all the dash lights come on, also if the heater is on at the same time as the radio and I apply the brakes the radio seems to loose volume and heater starts to slow down. Also when that happens all the guages go to zero and all the lights go off. Turn the radio or heater off and the lights come back on the speedometer starts to work again. The battery is brand new and all of the cables are clean and tight. I have checked every connection and all the grounds. I am wondering if it could the alternator or the voltage regulator? Any help would be great.

 

What can cause headlights, Dash lights, gauges and domelight's not to work?