My 2008 S60 keeps giving me the low beam failure error. Driver's side lamp seems to lose its connection. Jostling the socket seems to make the bulb go back on, but then of course, bumps and movement from driving breaks the connection within a day or two.

Is this a problem of not using enough bulb grease? I didn't think the grease had anything to do with maintaining an electrical connection, but just prevented the bulb from corroding.

Any recommendations for steps to debug this?

 

see if the socket/connectors have a crack. I've never (needed to) used "bulb grease" to improve a connection. You can use electronic cleaner or something to scratch off an corrosion - but the correct solution would simply be to replace the socket/connections as they can fail due to years of heat and moisture - particularly if you drive with your headlights on.

 

Disconnect it and look at the connector. Sometimes they melt. It'll be obvious. Sounds like you need a new connector.

 

I replaced the socket with an aftermarket one. It had two wires instead of the Volvo's 3, so I connected the two grounds from the Volvo to the single ground of the new socket. It worked fine for a week and now it's out again.

Possibly not coincidentally, I've also had an intermittent Low Tire Pressure/Tire Pressure System Failure light come one. That seemed to go away when I replaced the socket, though they could be completely unrelated.

Any suggestions for next steps before I have to bring it into a shop?

 

I am experiencing the same issue. TPMS warning comes on, sometimes with (passenger) low beam out, sometimes without. Sometimes they are both off and no warning lights. Guess it's time to do some socket checking.

 

I ended up having to get the whole headlight assembly replaced. Headlight is working, TPMS warning light is gone, too. Oof.

 

But the headlight assembly is just a plastic shell, or do you mean the headlight wiring harness?

 

Assembly and wiring harness, yep. Apparently you need to replace them all together. Volvo makes it difficult to get just the wiring harness. I dunno. It's working now, so...

 

Based on the frequency and range of electrical problems that show up on the forum, it appears that Volvo recruits engineering staff from a retirement home for Lucas and Magnetti Marelli veterans.

 

Lucas...AKA, "The Prince of Darkness"