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Old 08-09-2014, 03:48 PM   #1
Steve in OC OP
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Question about wiring a separate alternator light.

I am trying to install an Acewell, and it's going pretty well so far. But I need some advice about how to wire a separate alternator light.

I was just reading that long thread about installing an Acewell:

http://www.advrider.com/forums/showthread.php?t=527749

There are some posts in that thread that describe how to wire a separate alternator light. As I understand it, you get a standard 3 amp aftermarket idiot light that has two wires (I got a NAPA Echlin light http://www.napaonline.com/Catalog/Ca...A10_0006539451). Then you connect one of those two wires to a blue wire that comes from the alternator (the one that goes to pin 4 on the rubber connector block), and you connect the other to the green/black wire (the one that goes to pin 12 on the rubber connector block). Sounds pretty simple, but not simple enough for me, apparently. When I test-connected the wires of my idiot light to pin 4 and pin 12 on the rubber connector block, and then turned the ignition key to "run" position, the idiot light didn't light up. What could be wrong?
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Old 08-09-2014, 04:01 PM   #2
motor_chris
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Do you have a multimeter that you can use to check voltage at pin 4 and 12? Also make sure your handlebar switch is in the on position. I had no problem wiring in a light similar to this when I sent my instruments off for repair. You can also check the bulb by touching to battery.

motor_chris screwed with this post 08-09-2014 at 04:14 PM
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Old 08-09-2014, 04:42 PM   #3
Steve in OC OP
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Quote:
Originally Posted by motor_chris View Post
Do you have a multimeter that you can use to check voltage at pin 4 and 12?
Yes. My mutimeter says 12.54 volts at pin 12, and .24 volts at pin 4.

Quote:
Originally Posted by motor_chris View Post
Also make sure your handlebar switch is in the on position.
Yes, the handlebar switch is in the on position.

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Originally Posted by motor_chris View Post
You can also check the bulb by touching to battery.
The bulb comes on when touching the battery.
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Old 08-09-2014, 04:48 PM   #4
motor_chris
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Originally Posted by Steve in OC View Post
Yes. My mutimeter says 12.54 volts at pin 12, and .24 volts at pin 4.

Yes, the handlebar switch is in the on position.

The bulb comes on when touching the battery.
I am a bit stumped if all those conditions check out. Sometimes that connector can be a little tricky to make contact with the seperate light wires. Maybe a bit of a wiggle of the wires?? The only possibility if you have voltage is that somehow the proper current is not flowing, such as poor contact or connection.
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Old 08-09-2014, 05:16 PM   #5
Steve in OC OP
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What readings should I have gotten from pin 12 and pin 4?

I would be happy to connect the idiot light to somewhere other than the rubber connector block, if I knew where. I was just following the instructions in the Acewell thread as best I could, but I imagine there are other ways to connect the idiot light.
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Old 08-09-2014, 05:45 PM   #6
motor_chris
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What readings should I have gotten from pin 12 and pin 4?

I would be happy to connect the idiot light to somewhere other than the rubber connector block, if I knew where. I was just following the instructions in the Acewell thread as best I could, but I imagine there are other ways to connect the idiot light.
Your voltage reading seems fine, around 12V net. This is why I can't figure out what is going on. What voltage reading do you get going just between pin 4 and pin 12 and not going to ground?
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Old 08-09-2014, 07:03 PM   #7
Steve in OC OP
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What voltage reading do you get going just between pin 4 and pin 12 and not going to ground?
I get 2.45 volts.
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Old 08-09-2014, 07:34 PM   #8
motor_chris
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I get 2.45 volts.
That is why you have no light, voltage is too low. You have an issue to track down. You should have 12V there.
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Old 08-09-2014, 08:15 PM   #9
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Any ideas on what I should check first?
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Old 08-09-2014, 09:13 PM   #10
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It may be an oversight or perhaps it was an assumption - something like "all airheads are wired the same"? That's why there's no mention which bike this is?

Looking at the 77RS wiring diagram - terminal four has a blue wire leading to a connector and then to the diode board D+.

The other side is green with blue stripe and goes to the starter relay, coil, and then to the kill switch.

Verify all those connections are good, there's +12V coming from the kill switch, and shows up at the coils and starter relay.

Of course, your wiring may be different depending on which bike and year it is.
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Old 08-09-2014, 10:25 PM   #11
motor_chris
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Any ideas on what I should check first?
Since you measured 12V at pin 12 to ground, this would imply that the side connected through the ignition and to battery is fine. I would say start looking on the other side of the idiot light which is the charging circuit. Check the D+ connection at the voltage regulator, or possibly a high resistance in the stator. The current path should be from idiot light, thru voltage regulator, and thru rotor to ground.
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Old 08-10-2014, 06:08 AM   #12
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Yup. Good point. The BMW "ground" for the alternator light is not the conventional "touch it to a known good ground".... And may take some sleuthing...

If that system had been working properly prior to the new install (was it?....we don't know), the op prolly would not be stumped with the non-function situation.

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Old 08-10-2014, 10:18 AM   #13
Steve in OC OP
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Sorry I forgot to say what bike I am working on, Wirespokes! It's a 1976 R90.

I also forgot to say that the GEN light was working just a few days ago. After I got all my headlight wiring straightened out (with your help: http://www.advrider.com/forums/showthread.php?t=993430), I plugged the square rubber instrument connector block into my instrument pod, and the GEN light lit up.

OK, now back to the original question of this thread: why is the GEN idiot light not lighting up when I turn on the ignition.

As you all suggested, I need to trace the fault. Thanks to motor-chris' post, I focused on the charging circuit first. Since I have no idea how to test a charging circuit, I googled and found Snowbum's article on troubleshooting a dead alternator light. Here is the first part of that article:





"Troubleshooting a dead GEN lamp:
Because a common problem is a GEN lamp that does not illuminate at all, this troubleshooting section is first.
The problem may not be a bad bulb. The GEN lamp SELDOM burns out. More often it is the rotor that has opened, or connection where the lamp fits, occasionally the VR, and sometimes worn brushes. You can easily test the rotor without any instruments.
As a double check: Turn on Ignition....GEN lamp should still be out.
Disconnect battery (removing all the wires to the negative post will do).
Remove front cover.
Reconnect battery.
Turn on ignition. GEN lamp should still be out.
Pull off the wire/connector going to the brush holder male spade that is marked as Df.
Df is the place the lamp and VR both apply the initializing current (and, after the alternator produces current, where the alternator self-energizes).
Stick a bent paper clip into the wire/connector, and ground the clip to the case. The lamp should light up. If you do not have a paper clip, UNplug the associated wire, which is the D- female spade connection, and plug that Df wire into the D- female. D- is ground. If the lamp lights up when grounded, and not when to the Df terminal, then the rotor is open, or the brush(s) not making contact. If the lamp does not light up when grounded, it is the lamp, or the wiring or pod connector or the VR.
To further test for the lamp circuit condition, and eliminate the VR as the problem:
Turn off the ignition.
Pull fuel tank.
UNplug the VR.
Turn on the ignition.
Ground the solid BLUE female connection wire in the voltage regulator's harness socket.
If the lamp does not light up, the wiring from the VR to the pod or its large rear plug, or internal wiring or lamp or lamp connection in the pod is at fault.

Do NOT forget to disconnect the battery before replacing the front cover."
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Old 08-10-2014, 10:21 AM   #14
Steve in OC OP
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So, I followed his instructions: I unplugged the Df spade connector and grounded it to the case. And the GEN light lit up! According to Snowbum, that means the rotor is open, or the brush is not making contact. How do I test to find out which one of those is the problem?
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Old 08-10-2014, 10:39 AM   #15
motor_chris
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There is a picture of a rotor measurement about half way down the page in this link:

http://www.advrider.com/forums/showt...169507&page=60

This may not be possible to do with the alternator installed and the brushes making contact. I have also heard some people slip a piece of paper under the brushes to isolate them for the reistance measurement. Have you checked the wires ends going to and from the rotor (Df) for corrosion?

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