16.7v from the Alternator

rapt · 1 16.7v from the Alternator Mon Aug 17, 2015 5:21 am

rapt

active member

Number of posts : 29

So I have just re-assembled my K100 after stripping it down and got it started up after 6 months of being apart.

I was looking in to running a Lithium battery so I though I would check the Voltage.

The Charge voltage is sitting at 16.7v. This is much too high to run a lithium battery and more than likely too high for the rest of the bike.
I confirmed my meter was not wrong by checking it on a battery charger that was 13v.

Any ideas what could be causing this?

Dai · 2 Re: 16.7v from the Alternator Mon Aug 17, 2015 5:41 am

Dai

Life time member

Number of posts : 5720

Almost certainly a faulty regulator. However, before definately fingering the reg,

1.Check the alternator bulb on the dashpanel lights - it does light when you turn the ignition key on?
2. Before starting the bike, check that you have twelve-ish volts on the blue wire that connects to the top of the alternator (probably a redundant check because if the genny bulb is blown then there shouldn't be any voltage but... you could have a short circuit.
3. If 1 and 2 fail, pull the alternator and check the brushes for length or for being stuck in the housing.

92KK 84WW Olaf · 3 Re: 16.7v from the Alternator Mon Aug 17, 2015 5:55 am

92KK 84WW Olaf

Life time member

Number of posts : 7967

Dai

Spot on.

We had a discussion on that subject yesterday, being with some Honda owners. They fingered the effect of a faulty regulator in alternators like the BMW one as being exactly that, excess voltage.

rapt · 4 Re: 16.7v from the Alternator Mon Aug 17, 2015 6:14 am

rapt

active member

Number of posts : 29

Dai wrote:Almost certainly a faulty regulator. However, before definately fingering the reg,

1.Check the alternator bulb on the dashpanel lights - it does light when you turn the ignition key on?
2. Before starting the bike, check that you have twelve-ish volts on the blue wire that connects to the top of the alternator (probably a redundant check because if the genny bulb is blown then there shouldn't be any voltage but... you could have a short circuit.
3. If 1 and 2 fail, pull the alternator and check the brushes for length or for being stuck in the housing.

The gene bulb is either blown or has been knocked and there is no voltage on the blue wire with the ignition on and the bulb is not lit.

I relocated the bulb it to the inside of the fuse box so it lights up the fuse cover after I installed an acewell speedo when I first got the bike. I will remove the tank to check it tomorrow as it was working earlier on today before I started the bike.

Could a blown genny bulb cause the high voltage? From what I read it would mean the charge circuit would not kick in on most bikes.
I will also check the brushes tomorrow.

Dai · 5 Re: 16.7v from the Alternator Mon Aug 17, 2015 7:08 am

Dai

Life time member

Number of posts : 5720

Got it in one. A blown genny bulb will cause the high voltage because the regulator will never kick in.

92KK 84WW Olaf · 6 Re: 16.7v from the Alternator Mon Aug 17, 2015 7:55 am

92KK 84WW Olaf

Life time member

Number of posts : 7967

That's worth a Black Bush.....! For Dai.

Now wondering when will we get our first forum member visitor from NZ..

Dai · 7 Re: 16.7v from the Alternator Mon Aug 17, 2015 9:22 am

Dai

Life time member

Number of posts : 5720

Easy

Over-voltage = regulator, under-voltage = rectifier. Well, most of the time!

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1 16.7v from the Alternator Mon Aug 17, 2015 5:21 am

rapt

2 Re: 16.7v from the Alternator Mon Aug 17, 2015 5:41 am

Dai

3 Re: 16.7v from the Alternator Mon Aug 17, 2015 5:55 am

92KK 84WW Olaf

4 Re: 16.7v from the Alternator Mon Aug 17, 2015 6:14 am

rapt

5 Re: 16.7v from the Alternator Mon Aug 17, 2015 7:08 am

Dai

6 Re: 16.7v from the Alternator Mon Aug 17, 2015 7:55 am

92KK 84WW Olaf

7 Re: 16.7v from the Alternator Mon Aug 17, 2015 9:22 am

Dai

8 Re: 16.7v from the Alternator

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