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Old 10-13-2012, 05:53 AM   #1
photorider OP
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/6 idiot light help

With the weather turning colder my charge light seems to have gotten a little wonky. I'm pretty sure it's a bad connection at the big rubber plug behind the cluster because by pressing it, I can sometimes make it come on. Question: Without opening the thing up, does anybody know which pin goes to the charge light?
Thanks in advance.
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Old 10-13-2012, 06:08 AM   #2
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Quote:
Originally Posted by photorider View Post
With the weather turning colder my charge light seems to have gotten a little wonky. I'm pretty sure it's a bad connection at the big rubber plug behind the cluster because by pressing it, I can sometimes make it come on. Question: Without opening the thing up, does anybody know which pin goes to the charge light?
Thanks in advance.
See post #315 here http://www.advrider.com/forums/showt...527749&page=21 .
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Old 10-13-2012, 06:14 AM   #3
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Thanks, Craydds. Exactly what I needed!
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Old 10-13-2012, 06:30 AM   #4
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Quote:
Originally Posted by photorider View Post
Question: Without opening the thing up, does anybody know which pin goes to the charge light?
If necessary, it's not hard to remove instrument cluster, open it up, inspect/clean contacts, install a new bulb, etc. Best of luck.
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Old 10-13-2012, 07:12 AM   #5
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For the alternator to work the instruments are supposed to be in the circuit. Has to do with a resister I think and the voltage sent to the rotor. So with out the instruments there's no charging.

If you do open the instruments be careful with the tiny screws and don't over tighten when putting it back together.

The pins in the back of the cluster can be cleaned, same for the sockets in the rubber plug. Some have also compressed the sockets a wee bit to help them stay tight. They get mushed out after years. Have to be careful not to over compensate though.
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Old 10-13-2012, 05:27 PM   #6
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You might also read of a similar problem I ran into as well on my 75/6. Particularly post #62 and later. http://www.advrider.com/forums/showt...=798436&page=5

My problem, as you'll read, turned out to be a bad circuit board, specifically the connection between the pins and the thin copper(?) circuit board strips.

Good luck!

Lynn
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Old 10-13-2012, 07:18 PM   #7
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This will give you a good idea of the layout of the connections in the instrument cluster. Hope this helps.

http://www.p-thomas.com/shared/BMW/74%20R90%20Pod.pdf
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Old 10-13-2012, 08:14 PM   #8
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Wow! I wish that schematic were in my Clymer manual! I think I'll print that and stick it in with the bike wiring diagram.

Thanks

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Old 10-14-2012, 07:16 AM   #9
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wow! I wish that schematic were in my clymer manual! I think i'll print that and stick it in with the bike wiring diagram.
+ 1 !!!
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Old 10-14-2012, 07:22 AM   #10
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First time I've seen that diagram. It's a good one for sure. Anybody know who did this?
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Old 10-14-2012, 03:01 PM   #11
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First time I've seen that diagram. It's a good one for sure. Anybody know who did this?
That would be me. There is another one of the whole wiring 'map' for the 74 R90. It is here as an A3 PDF -

http://www.p-thomas.com/shared/BMW/7...0%20Wiring.pdf and looks like this -



Please note that the linked version has the stop/tail lamp wrongly labelled (gotta do something about that). The corrected version is available and if somebody wants to host it on their website, please email me.

My idea with these maps is that electrical bits should be placed roughly where they really are on the bike, hoping to reduce the mystery for newcomers to electrical circuits (like me). I'd really like to re-do this one, making it tidier and filling in the 'schematic' parts for switches and relays etc. I would also like to draw all the maps for the whole airhead range, but they take time - something for my retirement perhaps.

There is no copyright, so spread them around if you think they are useful.
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Old 10-14-2012, 03:11 PM   #12
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Thank you, Brun! Awesome!
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Old 10-14-2012, 03:46 PM   #13
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Brun,

Great drawings.

I have one suggestion. The coils have a polarity Neg - and Pos + side. They also have numbers one is 1, I think, and the other is 15, I think. Include these. I needed to find this info once and it took forever because most wiring diagrams don't have it. Now I'm no longer sure but I think the hot wire is Pos + and the black wire from the points is Neg -.
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Old 10-14-2012, 05:10 PM   #14
Brun
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Brun,

Great drawings.

I have one suggestion. The coils have a polarity Neg - and Pos + side. They also have numbers one is 1, I think, and the other is 15, I think. Include these. I needed to find this info once and it took forever because most wiring diagrams don't have it. Now I'm no longer sure but I think the hot wire is Pos + and the black wire from the points is Neg -.
Thanks Disston. That's the kind of stuff it needs. The reason I didn't include the pos and neg at the coils is that when I checked mine they were wired in the reverse of what the Haynes diagram indicated, and the bike ran just fine. (???)

It's also worth noting that some wire colours may be different. Wires from the left-side handlebar switches come to mind, but I don't remember off-hand what the difference was.
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Old 10-14-2012, 05:21 PM   #15
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Well of all the years I think 1974 is the one year that is only one year, isn't it?

I don't know why I think that's funny.

I saw another bike with the polarity reversed on the coils. It was at a Tech day and I tried to point this out to the owner and several people close by. They could not of cared less. So I gave up.

I would think the coils having a polarity means something but I don't know what that is. I do know I have been told since my earliest times around these things that it matters.

edit;
I just checked every manual I have handy right now. I couldn't find the polarity this time. But the hot wire, Green in earlier models later it's Green/Blue, is terminal 15 and the Black wire from the points is terminal 1.
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disston screwed with this post 10-14-2012 at 05:36 PM
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