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Discussion Starter #1
Hey folks, bit of a weird one this.

Started the bike up the other day (laid up over winter), left her ticking over to get up to temp and suddenly the headlight bulb goes off. I assume it's a bulb, but do a quick check of all other lights and the indicators (front and rear) on the left have also stopped, with no dash indicator. Right hand side works fine.

It gets a bit stranger, as before I shut her off, I give the throttle a few blips. Indicators and headlight both come on when the revs exceed circa 5k. As soon as it dips below, both stop working again. Any ideas? Possible relay or ECU issue?

Bit of back story if it helps. Had the bike off the road prior to September as the battery died whilst out on the road. Jump started it off a car and it made a bit of a pop, but everything seemed fine once it started. Replaced the battery, everything worked. Fitted new front indicators a couple of months ago, again, everything worked. Lives on a trickle charger, so battery should be fine (and is less than 6 months old).

So yeah, headlight and indicators have just randomly decided to pack in unless under load. I'm not massively knowledgeable on the electrical setup so any advice is appreciated.

Thanks
 

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Only at idle??? Check your charging system. Sounds like the SPU is having a low voltage problem on some of its relays.
What year 910 is yours? Early models had suspect SPUs...yours could be in the beginnings of failure mode.
 

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Discussion Starter #3
Only at idle??? Check your charging system. Sounds like the SPU is having a low voltage problem on some of its relays.
What year 910 is yours? Early models had suspect SPUs...yours could be in the beginnings of failure mode.
Esq'z; yes, only at idle or low revs. All start working again up once you hit that 4-5k rpm mark.

My 910S is registered 2008, but believe it is a 2006 with the infamous blue backed ECU (1.6m?) I've had cutting out issues since I've had it (4 years) when at 90 degrees and idling, so wouldn't be surprised if the ECU has been slowly dying...
 

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Well, it is not a Blue Backed ECU, that is the Service Power Unit (SPU) of which you speak....
 

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They are the usual signs of the SPU starting to go.
 

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Do a voltage check across the battery terminals at idle.......
Should be 14.5v+
Sounds like you lost a diode in the rectifier
Any automotive electrical shop can fix it, It's a ND car alternator
 

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Discussion Starter #8
Just a bit of an update; haven't touched the bike for the last month (Coronavirus chaos and all that), but decided to give her a wash whilst the weather was nice. Starter her up and all lights are working again.
Bit odd. Left her ticking over for 10 minutes, tried them again, still working. Few blips of the throttle, stopped working (left side indicators and headlight). Bit of a head scratch, few more blips, working again.

Doesn't seem like a loose connection, so I think it comes back to the SPU again. Tempted to give all the jack plugs a good clean first though, see if that solves it.

MVs are nothing if not whimsical creatures....
 

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That could be an earlier indicator of the SPU failing.
 
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