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Well my rush to get the bike running with a super-drained battery has cost me a voltage regulator. It's charging 15.8 volts, give or take.

So, before it completely ruins the battery, I need to do something. Can't find the Shindengen at the dealer, has anybody got a link? I know I bought this one on line but can't find the site.
 

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Well my rush to get the bike running with a super-drained battery has cost me a voltage regulator. It's charging 15.8 volts, give or take.

So, before it completely ruins the battery, I need to do something. Can't find the Shindengen at the dealer, has anybody got a link? I know I bought this one on line but can't find the site.
You are probably right Dennis but remember high resistance in the battery or battery connections can cause high voltages like that. If you checked at the battery did you put the probes on the lug itself and not the cables. Might take a minute to be sure. Might save you some money if you are lucky. Also be sure the wires that shunt the power to ground are clean. Seems to me I saw where people even added wires to shunt the excess to ground. I'll go see if I can find that for you, Buddy. :)
 

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Don't think a nearly-drained battery would hurt the regulator, if anything the extra draw from charging a low battery would lighten the load on a shunt regulator.

+1 on checking shunt grounds and battery connections...
 

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Don't think a nearly-drained battery would hurt the regulator, if anything the extra draw from charging a low battery would lighten the load on a shunt regulator.

+1 on checking shunt grounds and battery connections...
Measure voltage at the grounds to be sure it is near zero??? Voltmeter Red probe on green wires (2 greens at R/R) and black probe on battery negative LUG.
 

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Discussion Starter #7
Don't think a nearly-drained battery would hurt the regulator, if anything the extra draw from charging a low battery would lighten the load on a shunt regulator.

+1 on checking shunt grounds and battery connections...

The dead battery was just the start. I had to jump it from the car and the battery was so dead I needed to start the car. Jumping from a running car was the cause of this, I fear.
 

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The dead battery was just the start. I had to jump it from the car and the battery was so dead I needed to start the car. Jumping from a running car was the cause of this, I fear.
Contrary to popular belief I don't think that would bother the shunt regulator either. Even if a freshly started car was running at 14-15 volts and bike regulator went into heavy shunt, the shunting occurs on the AC side of the bike's rectifier bridge and the diodes block the car's voltage from getting there. So the bike regulator is not trying to shunt the car battery voltage, it is only shunting that which it normally does anyway - just the stator.....

I'd take the bike battery charge it up good and get it load-tested though. If it's on the verge of failing this can fool the regulator into high voltage readings, too.
 
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The dead battery was just the start. I had to jump it from the car and the battery was so dead I needed to start the car. Jumping from a running car was the cause of this, I fear.
I never heard of it causing a high charge, but I have seen it blow diodes. Doesn't take long either of both vehicles charging.
 

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Discussion Starter #11
First, thank you all for your help.

Okay, I'm not really clear on what I'm reading. Checking the voltage on the cable? You mean with the battery still connected but touching the cables and not the post with the meter probe?

And I don't get the shunt thing. Which wires do I ground for that?
 

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So, a blown diode won't cause it to overcharge?
No a bad diode will cause the alternator to put out less. Remember it does two functions. Regulator and rectifier. The stator makes AC voltage which will not charge a battery. The rectifier part changes the AC to DC so the battery can accept that. The regulator on your bike regulates the voltage so it doesn't get too high or low. Any voltage in excess of what its limit is will be shunted (Shorted over a resistor) to ground.
So the diodes (rectifier) change the AC to DC and the regulator throws away unwanted voltage. (regulator) Of course it needs a pathway to dump unwanted voltage. That is what the green wires are for. They carry unwanted power to the ground to get rid of it. Should be 2 greens. Check both the same way. If you pierce the wires and test with your voltmeter on AC it should read near near zero. If you see higher voltage there is an issue with the green wires or connections. Fix the pierce with some nail polish to keep the weather out. Are you using a voltmeter you trust?
 

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First, thank you all for your help.

Okay, I'm not really clear on what I'm reading. Checking the voltage on the cable? You mean with the battery still connected but touching the cables and not the post with the meter probe?
The other way around Dennis. If there was a bad connection between the cable end and the battery post you could have 15.6 volts from cable end to cable end but only 13 volts from post to post. The corrosion acts like a resistor and causes voltage drop. Go to the horses moth. Post to post. :)
 

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Dennis,
You should be able to measure the voltage across the battery terminals. There will be the battery voltage when the engine is off. If the charging system i shealthy you should see battery voltage at idle and then as the RPM increases the voltage will increase to about 14.1 volts. I have a good used stock regulator. I took it off my '85 last year when I did the stator. I put a Ricks stator and regulator on the 1200. Send me a PM if you need it. I will make you a good deal.
 

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So, a blown diode won't cause it to overcharge?
No, but it will introduce AC hum nor squeal into your electrics, as rectifier is compromised.

As I recall, there is a black wire leading to the regulator/rectifier that provides a battery voltage input ort signal to the regulator. If it develops a resistance through a terminal, it can report a lower voltage and the regulator pumps up output, looking to get battery voltage up to where it should be. Since it's getting a low signal, it may be seeing only 13.5 VDC when you check the battery with a separate meter and find 15.3VDC. There is a mod aimed at getting a truer reading to the regulator, involves a relay triggered by the former black wire. Below is the schematic I saw on it. My 1200 usually charged in 13.5 to low 14s usually, I was gonna do this mod.


Don't know if it'll help you.
Could it be that you are just seeing the results of a long eroding connection? I don't know. Regulators do fail on occasion.
 

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Discussion Starter #17
Turns out I still have the OEM off the '85 parts bike. Before I change it, I want to look at the suggestions I've gotten here, to make sure the one that's on there is really toasted.

I am a stickler for clean connections but I want to at least check first.
 

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Turns out I still have the OEM off the '85 parts bike. Before I change it, I want to look at the suggestions I've gotten here, to make sure the one that's on there is really toasted.

I am a stickler for clean connections but I want to at least check first.
I thought you would use the one off the parts bike. I get it about clean connections, but dirty connections will make the voltage lower. There are different ways a voltage regulator can fail. It is possible for the portion of the regulator that controls the voltage to fail and allow the full DC output of the alternator into the bike's electrical system. You are on the right track to check the output. place your voltmeter across the battery. Check the voltage with the engine off. It should read between 12v (dead battery) to 12.7 (fully charged). If you just ran the bike it might read higher, but it will go down after a few minutes. Then start the bike. At idle the voltage should read the battery voltage (or slightly higher). Rev the bike and about 3,000 to 3,500 rpm you should see the full output voltage between 13.7 and 14.1 volts. You should never see more than 14.1 volts. Just to be sure, all the lights are on and working while taking this voltage reading. If for some reason the headlight is out then the voltages can read higher. If you see more than 14.1 volts, the electrolyte will boil off and you will need a new battery soon. Check the voltages and if they are out of spec swap the regulator/rectifier and recheck. Let me know what you come up with.
 
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