My headlights (hi & low), signal turn lights, wipers,fog lights all do not turn on. My battery is approx. 4 years old. No corrosion, fuses are good. Engine turns over nicely. Just had new exhaust system replaced, new oil pan, runs well-I've not experienced any loss of engine power.Lights work inside the car and parking lights/reverse lights work. Any idea's as to what could cause this?