The circuit is designed to stop overvoltage to lights. It is not PWM until voltage goes over 13 and then it starts PWM to lower voltage. As voltage goes up the supply on time gets lower percentage. The frequency is 70 HZ (or is it 100 HZ) and that is high enough that the relay will not care. No luc...

Hmm, complicated. Starting in 2005 volvo changed to transistorized power supply to headlamps. Your 06 has transistorized power supply switching to headlamps and the circuit is monitored for opens and shorts. When problems are detected the CEM shuts off power supply for that key cycle. You need indi...