Hello, I have a 2005 Volvo s40 2.4i. So far I've noticed two ongoing issues.

1: While Driving (especially when turning the wheel, the radio flickers and headlights dim). Also while in park or slow speeds, the lights (headlights too) flicker, power steering goes out, gauges go crazy all while a small thumping/pulsating sound is heard.

2. Sometimes, when I go to start the car, nothing happens almost as if it's dead, sometimes I get a message stating: key error try again. This might be a faulty ignition switch, but I'm not sure.

Any help is appreciated.

 

Battery and/or alternator issue? Is your battery more than 3 years old?
If you disconnect a battery terminal when the car is running does the engine stall? If so, you likely have an alternator issue.

 

if you have a multimeter, do some quick tests - what's the voltage at the battery terminals - engine off (should be 12.5V or so). Now start the car. what's the voltage with the engine idling - should be 14V+. Now throw on the blower, lights, rear defrost etc. voltage at the battery should stay above 13.5 or so...

I'd be inclined to think you may have an ignition switch issue or a loose wire in the steering column. Next time you get the error message, try wiggling the key as well.