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Discussion Starter · #1 ·
I did a lot of tests on the motorcycle. The stator is working fine, the regulator was bad, so I changed the regulator. After changing it, the battery still would not charge. I did this test after changing the regulator:

Read the battery before cranking the engine: 12.5 volts

start the engine and let it idle, the battery reads: 12.2-12.3

side note: (the headlights and every light go dim when break light is used)

when engine is revved the battery voltage goes up by 0.1 volts

when turned it off and measured the battery again, it was 12.6 volts (I assume the battery voltage goes up initially and then goes down). Next day in the morning, I measured the battery again, and it was 11.99 volts.
What might be the reason the battery is not properly charging here?
 

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Have you observed any of this with the fuses pulled? If the stator and r/r are both good then as mentioned you should see higher voltage when revving up. Could have a short.
Has the battery been load tested? What kind is it?
 

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Discussion Starter · #4 ·
Its an AGM battery at at least three years old. I checked the fuses that are near the battery and they don’t seem to have a short. I tested the headlight by disconnecting it and it makes the voltage go up by 0.1, which is normal.
 

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Pulling the fuses is the easiest way to rule out most shorts. I would not expect to see the headlight dim with just the additional draw from the brake light without something else being wrong. My voltage drops to below 11.6 at an idle sometimes, especially after the motor has been running long enough to recharge the battery (which is new this year) but will put 13.5 volts out every so often while riding. Oddly enough the additional load from the fan or brake light does not trigger more output, according to the voltmeter anyway. I agree with the above suggestions but would like to know what each leg of the stator shows if the battery is ruled out.

In my experience the stator might show as fine but still not be 100%. I believe my stator is probably going to die one day, since as far as I know it is the original. In order to prolong its life I installed a MOSFET. Any particular reason you stayed with the regulator/rectifier?
 

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Discussion Starter · #6 ·
Pulling the fuses is the easiest way to rule out most shorts. I would not expect to see the headlight dim with just the additional draw from the brake light without something else being wrong. My voltage drops to below 11.6 at an idle sometimes, especially after the motor has been running long enough to recharge the battery (which is new this year) but will put 13.5 volts out every so often while riding. Oddly enough the additional load from the fan or brake light does not trigger more output, according to the voltmeter anyway. I agree with the above suggestions but would like to know what each leg of the stator shows if the battery is ruled out.

In my experience the stator might show as fine but still not be 100%. I believe my stator is probably going to die one day, since as far as I know it is the original. In order to prolong its life I installed a MOSFET. Any particular reason you stayed with the regulator/rectifier?
I tested the stator and it was fine, regulator wasn’t. So I replaced it, but it’s still the same, nothing changed. I did not pull the fuses, but I checked them with a multimeter and if I didn’t do anything wrong, they should be fine.
Would a bad battery not get any charge?
 

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If the fuse pull doesn't pinpoint a draw, try unplugging the RR and watch the voltage. A shorted RR is usually the cause of a current draw.

You can also unhook the battery overnight to see if the battery itself is discharging on it's own. AGMs perform very well and shouldn't lose anything overnight.
 

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Pulling the fuses is the easiest way to rule out most shorts. I would not expect to see the headlight dim with just the additional draw from the brake light without something else being wrong. My voltage drops to below 11.6 at an idle sometimes, especially after the motor has been running long enough to recharge the battery (which is new this year) but will put 13.5 volts out every so often while riding. Oddly enough the additional load from the fan or brake light does not trigger more output, according to the voltmeter anyway.
That doesn't sound normal.

You shouldn't see voltage that low at idle, unless the fan is running.

The fan normally drops voltage to near 12.5-13 or so. Voltage won't increase when more load is applied on this system.
 

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"That doesn't sound normal.

You shouldn't see voltage that low at idle, unless the fan is running.

The fan normally drops voltage to near 12.5-13 or so. Voltage won't increase when more load is applied on this system."

I agree. That is why I think my stator may be slowly failing. Although there are 2 other possibilities in my case. My voltmeter is hooked up to a "key on" 12 volt source on the 8 pin connector. I don't recall which one but I was in a hurry and did not install a relay to get direct battery voltage. My voltage seemed correct when I was hooking everything up with the engine off but I don't know if it is accurate when running. Also my voltmeter is the one that the lense melted on in the sun. Could be cheap and inaccurate. New one is on the way with a relay. Since the battery stays well above 12.7 volts when checked directly I suspect a gauge/wiring issue.

To the OP. I also want to know your stator readings, If you are looking at DC and not AC you could have a bad stator. Did you load test the battery?
 
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