Some newer vehicles have 2 headlight relays.One for low beams,one for high beams so check for a faulty relay first.If you only have one relay for headlights,its probably good since your low beams work.Its rare for both lights to blow at once(driver and passenger side)but your bulbs might be bad.Some vehicles have a seperate bulb for high and low beams and other vehicles have just one bulb for high and low beams.The dimmer switch you move to change from high to low may be faulty too.You didn't list your vehicle make/model so I'm not sure exactly what type of switch you have.It may be a fault in the multi function switch,which includes the signal lights dimmer switch and windshield wipers(if this is the type of switch your vehicle has)You can remove the headlight relay and test for voltage at its connecter.If no voltage,the problem is between connecter and switch or connecter and battery.You can swap another closeby relay with same part # in existing relays place to see if it fixes fault
