'05 V70 2.5T High Beams died completely - looking for tips on wiring/design Topic is solved

timetobakethedonuts · Post by **timetobakethedonuts** » 30 Jan 2021, 19:04

Tonight, I very quickly flipped my high beam switch a few times while driving, and something apparently blew. Now, the high beams do not work - neither the lights or the blue indicator on the dash. There is no "click" when I pull on the lever. Nothing.

I started by considering the switch (stalk) may have gone bad, and I see that replacing would be fairly easy. But I am not confident that it will contain more than contacts - which could be the cause but I suspect not. In looking for a relay for the headlights, I found to my disappointment that none of the roughly 7 relays in the engine compartment are for the headlights. I have not yet checked the L or R high beam fuses (I will do that just to eliminate this as the cause), but in doing some Googling, it appears that there may be a relay in the CEM (module).

From what I am reading, there may be wiring diagrams somewhere (eg VIDA) that can help me diagnose the issue by showing what is in the headlights circuit. I am capable of repairing modules (if not sealed hermetically), but I don't want to go removing the CEM if it isn't necessary. I have seen comments that a wiring diagram may show a relay, but not depict that it is inside the CEM.

I am hoping someone here may have access to the wiring diagram for my model, and verify if there is a relay in the high beam circuit. Also, if there is any indication where such a relay is located. Thank you in advance, Don

Post by **darrylrobert** » 31 Jan 2021, 02:53

CM14 is high beam relay in engine bay *correction passenger compartment that is under the steering wheel

: high beam relay; cm14.jpg (161.11 KiB) Viewed 2692 times

Post by **darrylrobert** » 31 Jan 2021, 03:04

Sorry ignore above, looks like 2005 in a Mosfet on the CEM PCBoard. are you handy de-soldering tiny components?

timetobakethedonuts · Post by **timetobakethedonuts** » 31 Jan 2021, 10:56

darrylrobert wrote: ↑31 Jan 2021, 03:04 Sorry ignore above, looks like 2005 in a Mosfet on the CEM PCBoard. are you handy de-soldering tiny components?

Thank you, that is part of what I am looking for (you had me excited at first thinking it might be a relay I was not aware of!). If someone is capable of and it isn't a violation posting a snippet of the schematic/wiring diagram that shows said MOSFET that might be helpful. There also may be circuitry in the stalk as well. There has to a latch (latching relay or circuitry) somewhere that keeps the high beams on when the HL dash switch is in the on position.

timetobakethedonuts · Post by **timetobakethedonuts** » 03 Feb 2021, 18:02

darrylrobert wrote: ↑31 Jan 2021, 03:04 Sorry ignore above, looks like 2005 in a Mosfet on the CEM PCBoard. are you handy de-soldering tiny components?

I have no idea who has access to what sources for wiring diagrams - can a DIY person get them at reasonable cost?

You appear to have a resource that you consulted. If I dig into the CEM, my guess is I will find multiple power devices. Can you tell me if you see a reference designator on that MOSFET - such as Qxxx or Uxxx? In the event I take it apart, and the circuit board is marked, this would help me identify the correct part.

My alternative at the moment for a short term fix is to wire the fog light power to the high beams. I *really* don't want to go this route, and it will be a matter of necessity to have it fixed correctly if I get into a situation where DMV requires me to have a safety inspection. The fog lamps draw 55W vs 65W for the high beams, so there is a chance I will get away with it. Another thing you could check for me would be, do you see if the fog lamps are also driven by a MOSFET in the CEM, and if there are part numbers shown, are they the same? That would give me confidence each circuit can handle the high beam power.

Post by **darrylrobert** » 03 Feb 2021, 18:37

Sorry i cannot answer the Mosfet question for you, however i was thinking if the stalk switch isnt Can-bus and you found the trigger pin/wire for the stalk switch , you could wire in a relay. You would likely need to hack the DIM "blue" LED light, ive done that and its easy.

timetobakethedonuts · Post by **timetobakethedonuts** » 03 Feb 2021, 20:13

Yes, I was thinking of that also - that I could control a relay from the stalk switch. It didn't occur to me that it may be on a CAN bus, which would nix that idea. Cars have become so complicated since the 60s - ha ha. I really hesitate to dig into this without any schematics, other than my idea of using the fog light switch to control the high beams. I never use the fog lights - I have found them essentially worthless. It had occurred to me that the blue indicator would not work, and yes I could hack that but how much work would this be - would the dash have to come out, etc. The stalk plugs into about a 9 or 10-pin connector that is integral with the steering column - I don't know that I could even get a scope or DVM on the pins to try to reverse engineer or understand it.

What documentation were you looking at that showed the MOSFET - a detailed schematic, or something simplified like perhaps I have seen in some fancy code readers, or something else? I know an an indy mechanic - maybe he has access to licensed VIDA software.

timetobakethedonuts · Post by **timetobakethedonuts** » 03 Feb 2021, 20:27

darrylrobert wrote: ↑03 Feb 2021, 18:37 Sorry i cannot answer the Mosfet question for you, however i was thinking if the stalk switch isnt Can-bus and you found the trigger pin/wire for the stalk switch , you could wire in a relay. You would likely need to hack the DIM "blue" LED light, ive done that and its easy.

I just watched a YT video on VIDA/DICE, in which the author advised getting one of these - he said they are $50-70 on Ebay though he did question their authenticity. In the video, I saw a "wiring diagrams" menu choice. This tool may be the way to go if an account isn't needed and the diagrams are embedded in the software.

*edit* I found another commentator who in 2017 wrote that the wiring diagrams were NOT included with the VIDA DICE he bought (only one disc came with it), and a second disc was found on Ebay that had the diagrams, and it worked when he added it.

Post by **June** » 03 Feb 2021, 22:59

Don't rule out the switch. Mine just broke on my 04 last month. So it is possible the switch died. The dealership charged me $220 to replace it. My high beams died as well. June

timetobakethedonuts · Post by **timetobakethedonuts** » 04 Feb 2021, 00:00

June wrote: ↑03 Feb 2021, 22:59 Don't rule out the switch. Mine just broke on my 04 last month. So it is possible the switch died. The dealership charged me $220 to replace it. My high beams died as well. June

Hey that is good news, and I found someone else with a similar report as detailed in this text I was preparing when I saw your comment. Question - did the blue dash high beam indicator NOT illuminate when the defective stalk was pulled?

For anyone who finds this thread in the future and has no high beams or indicator, here is the post where the OP reports the same symptoms, and at the end of the thread he returned to say it was his stalk that was the problem: https://volvoforums.com/forum/volvo-xc9 ... ing-86008/

It appears that the VIDA DICE product is designed to work on Win 7 Pro, but people have figured out how to make it work on Win 10 by jumping through some hoops. Neither one looks quick and easy to me. There is also a VIDA software only product out there, which has wiring diagrams but no hardware. If you are a company, for $3.50 you can get a 3-day subscription for wiring diagrams through Volvo, which for up to MY 2015 or 2016 you can view these without VIDA. But I am not a company.

I also found a few complaints similar to mine. In one of them, the person tried replacing the stalk and nothing changed, but he ultimately found out the used stalk he bought was bad and his issue was in fact the stalk. Someone reported that the stalk can be fairly easily disassembled, and contacts inspected. Multiple people report that VIDA/DICE can turn on the high beams - which would point to whether the CEM electronics are OK or not.

I found a sample of the low beam/high beam wiring diagram for an unknown model/year Volvo, and in fact it shows CAN-bus signals going to and out of the CEM, as well as a transistor symbol to indicate a driver. This is likely the kind of source that darrlyrobert cited. So a strategy is beginning to take shape. If my Indy can exercise the CEM high beam circuit, that would test that. I can remove the stalk fairly easily, and inspect it from the way it sounds. There are some discrete electronics on a circuit board in it, in pictures I have seen. Worst case I can break down and get a DICE running. Actually, worst case I could pay the stealer to diagnose the issue, and repair it myself. I appreciate the replies.