I have an issue that I've seen come up frequently in these forums and elsewhere, but there never seems to be a clear resolution or steps taken.

PROBLEM: About a year ago, my driver side low beam failed. I suppose it was a week or so before I noticed the foglight on that side had also failed. I replaced the bulb, noting that it was odd the old bulb would still light up with 12v, and it remained failed. I put the original bulb back in and began checking fuses in the engine compartment and side driver side dash in the cabin -- nothing was blown. I replaced anything that seemed headlight related just for kicks, but to no avail. I pretty gave up and decided to deal with it at some other time. A few weeks later the turn signal marker light in the same driver side headlamp assembly failed. I've gone back to check the bulb, check fuses, stare at undocumented relays, and found very little current (if any) being received by the low beam harness/plug when read with a multimeter (cheap, 0.01v when expecting 12, autoranging might be giving it the 0.01v anyways). I have moderate experience with electronics, but mostly PCB boards and not cars. I'm not sure where to stick my probes next (no pun intended) and I have no idea what any of these relays are for since they left that out of the owners manual. I'm not finding an easy way to test relays other than noticing they still look brand new, but that's mostly because I'm trying not to set my car on fire or destroy the electrical system with my 'applied electrical experience' (from smaller consumer devices to a car).

Does anyone have a wiring diagram for the 04 S80 2.9 (even if just as it pertains to the front headlamp assemblies to get started)? Or any other suggestions based on the information above? It would be much appreciated as my local Volvo dealership (where the car was purchased) just keeps charging me money I don't have to not fix the problem and then getting awful rude when asked for at least some observations. No more .. of them.

Thanks in advance, tech, i mean, ANYONE.

BTW -- I didn't even notice the data logging interface under the dash until the other day -- a pinout diagram to interface with that would be sweeeeeet, but having 2 low beams and the turn signal (and maybe even the fog light) would be sweeter

 

I just noticed someone with a very similar issue that tech responded to and the owner of the troubled volvo (amazingly! thanks!) followed up with what was wrong. I'll check into this and follow up, (under driver dash), but if anyone has any other ideas in the meantime, I'm all ears as I've let this go for like... a year.

 

Because I keep replying to my own thread, I'll post the CEM (front dash) diagram I found for the 04 S80 (if anyone else is interested). I saw others posted, but not this one (i miss quite a bit though)

 

The local dealership sells the shunts for about $7 (amazingly). I took the shunt from my rear fogs and replaced the low beam shunt in the CEM and was able to get the previously non-functional low beam working -- sort of. Now, with high beams, the passenger side high beam doesn't switch off and the driver low beam only works with the highs on (and the high beam no longer works). The bottom of the shunt seems loose -- I'm having trouble pulling the CEM out to work on/clean/inspect despite others describing the process. Anyone know of a picture by picture (i know, lame) description?