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I'm not gonna lie; I'm no electrical expert... but I'm confused by this.
Sidelights and main beams are fine. Dipped headlights are not working.
The wires were all looking knackered and frayed. The earth seemed intermittent, too. Unfortunately, the original earth was too small and tucked away to be able to tag to it so i made a new earth for it attached to the body. Checked with multimeter - continuity to the battery negative terminal. Checked the live - 12v when switched on. Plugged in bulb - didn't work! Hardwired bulb to battery and it's fine.
So - the bulb (H7) has 12v and ground and doesn't come on.... anyone able to shed shed light on this issue? My understanding of basic electrics has been tested here!
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ChasR
RR Helper
motivation
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Club RR Member Number: 170
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Volvo v70 headlightsChasR
@chasr
Club Retro Rides Member 170
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If it has a CANBUS system it will be smart ; it will know that you are trying to short the bulb to ground. The only way to get around it is to repair the correct ground, or send another ground to the original location.
IME CANBUS systems have earthing points in the car for various systems ; this is how it can determine what is wrong and how it it is wrong.
If it were me I'd see if the fuses are OK. If they are at all suspect change them for new ones. Check the connections next. See if it works. If not go over the wiring with a fine tooth comb.
CANBUS systems aren't too horrendous when you 'get' them but the explanation is normally very poor. I only vaguely started understanding them when my dad fixed a similar issue on a Mondeo of ours.
It could also be that the switch is knackered.
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Last Edit: Dec 6, 2017 22:32:03 GMT by ChasR
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Thanks Chas - sounds like it could be it. Also sounds complicated and frustrating! Switch seems to be working
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ChasR
RR Helper
motivation
Posts: 10,201
Club RR Member Number: 170
|
Volvo v70 headlightsChasR
@chasr
Club Retro Rides Member 170
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My dad has cut his teeth on electrics for years and often solved a few issues, both at home and on the cars. I'll give you this example. We have a 2007 Mondeo 2.5T at home. 2 years ago, maybe 3, it started randomly opening the bootlid, or rather the car thought it was. We would slam it shut etc and despite it being closed it was fine. One day literally 3 days before an MOT we noticed the rear number plate lights and fog lights didn't work, along with the tailgated sidelights, the body ones were fine. I changed the bulbs and despite some of them looking on their way out they still didn't work! My old man against my wishes then put another earth in. That didn't do anything! We go out Forscan and read the codes. They went as follows: - Rear fog light open to ground
- Rear number plate lights open to ground
- Rear Number plate lights short to ground
The last error was down to us. This is why I say code readers can be handy . I tried tracing the wires back to where it should be, looking for an earthing point to clean. We then stripped out the boot. Eventually we found all of the earths went back to central points as I said earlier. We then checked the boot wiring again. It was only when we completely stripped the tailgate to its bare bones that we found the fault ; the wires had pinched hence why the boot saw itself as open and the lights were off. We put in some more flexible wiring and all was well. We even managed to fix the cruise control ; the boot claiming it was open kept on knocking it off . Basically, bodgery will only get you part of the way in most cases and moderns won't tolerate it unless you go back to a true source.
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Last Edit: Dec 7, 2017 8:10:54 GMT by ChasR
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