Battery Not Charging - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 05-18-2011, 03:33 PM Thread Starter
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Battery Not Charging

My battery keeps dying, I know its that because the bike will run great if I toss it on a charger for quite some time, but eventually it will lose enough charge to not start. However, even when the battery is dead, if I jump it it will run fine.

I'm trying to figure out if it is my stator or maybe the R/R. (or something else?)

I found the stator testing procedure. The ohms between each coil is the same and under 2. None of the three yellow leads is grounded out. The question I have is what should the voltage be with the engine running? I keep seeing 50V but no one says what RPM that is at. I get about 19V at idle but when I rev her up I see 50 and up to 70 (not revving above 5-6k). Is this an acceptable reading? If it is then it isn't my stator.

There appears to be no good testing procedure for the R/R. However, I have seen many posts saying that is a good mod. I don't know what else could be failing in the charging system so should I just go ahead and assume the R/R?

Also, I have disconnected all of the plastic connections between various pieces of the electrical system and used electrical contact cleaner and a steal cleaning brush and reconnected everything.

Thanks for any input


1993 Kawasaki Vulcan 750
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post #2 of 8 (permalink) Old 05-18-2011, 04:35 PM
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Checking the voltage at the battery, This is verbatum what my VN750 service manual says. 1). "If the output voltage does not rise as the engine speen increases then the R/R is defective or the alternator output is insufficient for the loads".
In the manual there is a resistance check that you can do for the R/R, let me see if i cant explain it to you. First of all we need to lable the contacts on the R/R with the connector removed. Make a small drawing for a referance. Top row from left to right contacts are; A1, A2, A3. Bottom row from left to right contacts are; G, M, B. For doing your readings meter polarity matters, so (-) means negitive meter lead and (+) means positive meter lead. Again these are resistance readings so all reading are in OHMS. By the manual if the readings are higher then specified or lower them specified, replace the R/R.

(- B) to (+ M, G, A1, A2, A3) = no continuity, infinity.
(- M) to (+ B, G, A1, A2, A3) = 10k to infinity.
(- G) to (+ B) = 0.4 to 2k, (+ M) = 1 to 5k, (+ A1, A2, A3) = 0.2 to 0.6k
(- A1,2,3) to (+ B) = 0.2 to 0.6k, (+ M, G) = infinity.

Last edited by ifixf18s; 05-18-2011 at 04:47 PM.
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post #3 of 8 (permalink) Old 05-18-2011, 05:03 PM
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If you call the three yellow stator leads A,B and C; and get 50-70 VAC with all three combinations AB, AC and BC between 5-6k RPM, I agree that the stator is putting out an acceptable charge.

If your r/r doesn`t check out good, I would go with the Shindigen/mosfet replacement you link to in the first post.
It will charge at a constant 14+ VDC from idle speed of 1100 rpm to redline.

Use some dielectric grease to seal your newly cleaned electrical connections.


1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15

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post #4 of 8 (permalink) Old 05-18-2011, 06:07 PM
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+ 1 on the MOSFET R/R upgrade. I just did mine last week. I relocated mine to in front of the top of the radiator just below the triple tree. I made a custom bracket to hold it. Nice cool air upfront to cool a MOSFET R/R that doesn't get very hot anyways = many years of reliability....hopefully. My Rick's motorsport stator is 1.5 years old and still holding strong. The new MOSFET R/R charges at 13.0 volts at Idle and 14.0 volts at 4500 rpm on my Deka AGM Battery.
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post #5 of 8 (permalink) Old 05-18-2011, 06:55 PM
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Your stator voltages look good to me...... could be the R/R or wiring between the R/R and battery. You haven't mentioned your voltage at the battery at different RPMs....
The MOSFET is a great replacement, if your R/R is bad.....not too hip on relocating very far away thou. IMHO, the stock mounting location is fine for the MOSFET. Better without the goat belly, of course.
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post #6 of 8 (permalink) Old 05-18-2011, 10:56 PM
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**DARIV** is correct....If you go with the MOSFET R/R you DON'T have to mount it up front like I did.....I am just anal about keeping the R/R cool. You can mount it in the Factory location.......UNLESS you plan on keeping your Goats Belly......the Heat rising 2 inches off the goats belly is what I think is the MAIN reason that our R/R goes bad......The R/R has heat sink fins to dissipate heat......not collect it from the goats belly(which gets extremely hot)!!!! right under it. This was a horrible placement in design from Ma Ma Kaw. If your going to keep the goats least mount you R/R on a bracket behind your left side passenger peg. Let it at least have a fighting chance to get some cool air. Electronics are DESTROYED by two main things...... 1. Overheating and 2. Dust/Dirt/Water

Last edited by BRET H; 05-18-2011 at 10:59 PM.
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post #7 of 8 (permalink) Old 05-19-2011, 01:32 PM Thread Starter
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Thanks for the quick replies! I did the recommended measurements

-B to +M, +G gave infinity; but to +A1,2,3 gave 9k
-M to all gave infinity except to G which gave 16k
Thus didn't seem too weird

Then -G gave infinity to everything; I'm guessing this is a clear indication of my problem

Also +B, +M, and +G to any of the As all gave infinity as well.

Guessing I should bite the bullet and replace the R/R eh?

Also, I haven't investigated the goat's belly removal too much. Can I remove it without having to replace the pipes or is it an all or nothing situation? I'm a broke student so I'm not looking to spend extra money... the 100 on a new R/R is bad enough!

Thanks all!!!

You guys always help when my bike is acting up, and fast!

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post #8 of 8 (permalink) Old 05-19-2011, 02:12 PM
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keep the Goat (it will cost you to remove it and fix the mufflers right).. relocate the new R/R (can be done very cheap)
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