2005 1200GS ABS - smoke from electrics wire from alternator

[seags]

Hi all, had the tank off to give the bike a once over before the season starts and connected the battery which had been off the bike for a few weeks. When I reconnected the battery there was a big spark from the battery terminal and smoke came from melted insulation from the alternator area. I have found a wire that has melted, its the one that goes from the alternator to a small cone shaped device that is bolted to the side of the alternator. I assume what ever this device is has cause a short circuit as one end id earthed to the alternator and the other is connected to the positive terminal of the alternator that is also connected to the starter motor. Any know what the cone shaped thing is and what could be the problem?

Cheers

 

[(RIP) Miff]

Could you post a picture up??

 

[(RIP) Tunneruk]

Are you 100% sure you got the battery polarity right?

 

[DrFarkoff]

Are you 100% sure you got the battery polarity right?

Wot He says !

 

[Delboy777]

Id say not, probably wrong way round.

 

[trainman]

Hi all, had the tank off to give the bike a once over before the season starts and connected the battery which had been off the bike for a few weeks. When I reconnected the battery there was a big spark from the battery terminal and smoke came from melted insulation from the alternator area. I have found a wire that has melted, its the one that goes from the alternator to a small cone shaped device that is bolted to the side of the alternator. I assume what ever this device is has cause a short circuit as one end id earthed to the alternator and the other is connected to the positive terminal of the alternator that is also connected to the starter motor. Any know what the cone shaped thing is and what could be the problem?

Cheers

its a diode, or one way DC gate if you like, if you connected battery back to front then the batt -ve would be on the wrong side of the diode and travel through returning to +ve which is now the case of the alternator thanks to the mis wiring, the wire being the thinnest part of the loop has melted first

if you haven't done this then the diode maybe short circuit

 

[seags]

You sir are spot on, I had only done it for a second but I had got the battery wires crossed. I think the item is the voltage regulator so will probably need a new one.

Are you 100% sure you got the battery polarity right?

 

[seags]

Does anyone know if you can buy these diodes separately from the alternator as it is external to it?

 

[trainman]

You sir are spot on, I had only done it for a second but I had got the battery wires crossed. I think the item is the voltage regulator so will probably need a new one.

from memory its a zener diode, as you say even if the wire is repairable and the diode ok (which it might be) a new one is best all round and assuming BMW come up with a daft price for it some car electrical places specialise in these parts and you should be able to get one cheaply - get on the google!

 

[Bendy toy]

Electrex might have a suitable replacement. I cant see anything on their website , but you could ask if they can offer a new regulator for the R1200.

http://www.electrexworld.co.uk/acatalog/Contact_us.html

 

[trainman]

Does anyone know if you can buy these diodes separately from the alternator as it is external to it?

yes for sure, I believe its actually a protection device and its not the main regulator/rect (these bits are inside the main case), I don't think you will have damaged the insides but you will find out once you have changed the diode and started her up!!

http://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=10&M=35&Ct=IA&SbCt=BA_10_35_IA_10

if you look at link, 2nd item from bottom, this shows what you have, although your alternator is probably Bosch so you need the equivalent version

 

[seags]

Hi all,

Can I just say thanks for all the helpful comments, especially the link to mw which is exactly the part I need. Believe it or now I consider myself an experienced home mechanic and have rebuilt several bikes and cars however todays muppetry will have to go down to a senior moment!

 

[(RIP) Tunneruk]

Hi all,

Can I just say thanks for all the helpful comments, especially the link to mw which is exactly the part I need. Believe it or now I consider myself an experienced home mechanic and have rebuilt several bikes and cars however todays muppetry will have to go down to a senior moment!

You're welcome fella, if it helps, I do this for a living and last year while kneeling next to a bike I blindly reached down for my soldering iron and promptly picked it up by the red glowing end!!

 

[seags]

Ouch, that must have hurt. Once again thanks for the help.

 

[Bendy toy]

I had a bike battery fail while I was out riding. I got home fine, but came to start it 2 hours later and battery was dead flat. Big deal it happens.

I got a new battery but it sparked when I connected the leads (it wasnt possible to get them wrong). I pulled all the fuses and it still sparked. Hmm??? The sparking stopped when I disconnected the alternator. The V-Reg had gone short circuit and cooked the old battery. It had no diode protection so I had to fit a new alternator.