My wife and I recently purchased our 2001 S60 with approximately 132,000 miles. The driver side headlights, low and high beams are brighter than the passenger side. I used my test light to check grounds and all appears fine on both sides. When I checked the test light on the positive battery terminal it was fine, when I check the lights on the drivers side with the test light its extremely bright, any ideas?

 

I know this is a dumb question but is the actual headlight fogged over or anything on the dimmer headlight? Or is it even the original headlight that you know of?

 

I wondered as well, except the test light is brighter on the drivers side as well.

 

Sounds like you have excessive resistance in either the HL feed or ground wire on the passenger side. Do you have a voltmeter? Test light will not give you the accuracy you need.

 

What is the HL line ? I agree about the test light and a need for a voltmeter. Is it possible to get more voltage than necessary to the drivers side light? The test light shines at the same brightness when testing the positive battery terminal as the passenger side lights?