Hello Everyone,
I genuinely did not want to get acquainted with an electrical problem, but here goes.
I have a 2003 Volvo s 40 that has been really trouble free , but my passenger side low beam headlamp no longer works. Just died without advance notice, As it stands: Brand new fixture, fuses and bulbs good and tested by direct replacement. Voltage on both hot pins, 3 pin female headlamp connector.socket. If the return/ ground were bad then the high beam lamp would not work. If there is approx. 14 unloaded DC volts on both hot pins with high beams on, why does the low beam bulb not light? Is there a malfunctioning voltage regulator board for each headlamp high/ low beam bulb that I don't know about ? The cable that feeds the headlamp disappears into a bundle and there is almost no room to get a probe on any part of the wiring.
I thought about just splicing in a new wire from one headlamp to the other, but thought it was crass and wrought with problems like too small a fuse or back feeding dc to something that shouldn't be back fed.
Tried to find a schematic on lne for the car, but there doesn't seem to be one.

Many Thanks,

Bob Hodge

 

low beams go through the CEM, high beams do not. You may want to check the voltage at the CEM or consider replacing the CEM (it hides under the dash right above the hood release lever (the box with three electrical connectors going into) The gen 1 S40 CEMs are not paired to to the ECU so you can buy a used one for about $75 and swap it in in about an hour or so.

Wiring diagrams are available online - just google "Volvo S40 wiring diagram" or Volvo V40 wiring diagram etc.

 

MANY MANY Thanks !!!

Bob

 

Yes, I've had to replace several CEMs to solve the one headlamp not working problem on the early s40. They do not require a software download to work like other Volvos - so it's plug and play if you bolt in a new/good used one or get someone like xemodex to fix yours.

 

Thanks very much !
I was pleasantly surprised to find that the headlamp started to work after removing the under dash cover that needs to be removed to access the CEM. Yesterday it didn't work at all. So tomorrow I'll exercise the 3 plugs and see if it still works And maybe if I'm lucky that will fix it. But if the problem returns I'll know where to look. By the way, I saw another panel with what look like plug in relays next to the CEM. Do any of those have anything to do with the headlamps ?

Thanks to both of you ! Maybe some day I can return the favor.