Kawasaki VN750 Forum banner

Back again...low charging voltage

2K views 32 replies 4 participants last post by  mmart 
#1 ·
I'm back again with an update. I still don't see >13V when riding. I installed the MOSFET R/R (wow, very straightforward install! it went very well) and also performed the blue wire mod (wow...even more of a straightforward mod). I finished an hour long ride today and my battery reads 12.54V. That's over 90% charge, not bad!

However...

As soon as I flip the key to on (engine is still off), this voltage drops to 12.12V. Could it be an issue with the Junction Box? Could it be my onboard voltage meter attached to the turn signal wiring causing an issue? (I'm grasping at straws here I feel like, haha).

This issue existed prior to my MOSFET install. Any thoughts as to what's going on here? In a previous post I share the results of my stator test and the stator checks out, so I don't think it's that. Something else perhaps is going on here.
 
#3 ·
This is great for my own understanding as well, thank you for that insight. I do have standard filament headlight bulbs and turn signal (front) bulbs. Only the rear turn signals and brake light are LED (combination unit). So this makes sense.

What doesn't make sense is why with the new MOSFET R/R I'm not at appropriate charging voltage (~14 to 14.5V) when I'm riding at speed. My onboard voltage meter (again, connected up to the turn signal wire in the headlight assembly) only yields me ~12.5 or 12.7V at speed. I'll check it again later with my hand held volt meter directly on the battery while revving (maybe the onboard voltage meter isn't calibrated correctly).
 
#5 ·
My voltmeter is hooked up to my accessory leads as well and it’s not the greatest voltmeter either but it works. Sometimes it’s off a few tenths of a volt when I compare it to my multimeter across the battery.
You could pull out the fuses for the lights/accessories and start it to se if it yields any different numbers a different rev ranges.
 
#6 ·
My voltmeter is hooked up to my accessory leads as well and it’s not the greatest voltmeter either but it works. Sometimes it’s off a few tenths of a volt when I compare it to my multimeter across the battery.
You could pull out the fuses for the lights/accessories and start it to se if it yields any different numbers a different rev ranges.
I'll try this and report back with updates. Thank you.
 
#7 ·
12.7v at speed is really low.., especially if the fan is off. Something isn't right. That's practically no charging at all but there must be some output because it's keeping 12.7v with all the lights on.

Tanner had an all new charging system and wasn't making good voltage. The Two Wire mod fixed it.

I hate to bring up another mod, but something is pulling the voltage down.

I don't know if it would help to pull fuses while watching the voltage, engine running. Maybe...
 
#10 ·
If I’m in traffic and the fan kicks on my bike will show 11.x on the meter if I’m sitting for a while. My idle is right around 1000rpm. As soon as I can move and get on the throttle the meter jumps up to 13.x. The highest I’ve seen on it is probably 14.2 on my dash meter which probably translates to 14.5 directly at the battery. This takes into consideration the cheap onboard voltmeter and any loss across the bikes wiring through the accessory leads.
 
#12 ·
If you pull a fuse and voltage rises significantly, that circuit has a problem. A minor rise is expected because lights may shut down, etc.. This test may not prove anything.

The mosfet install bypassed all the old RR wiring, correct? I'm trying to think of where the short can be.

With a good stator and mosfet kit, you should be able to remove the positive wire coming from the mosfet at the battery and read really good voltage on that wire, like 13.5-15v. So try that. I think that should prove if the system works or not.

If it has good voltage there, then we have to look at the battery and electrical system.
 
#13 ·
Yes, the MOSFET regulator bypassed all the old R/R wiring.

I pulled fuses and found that with the headlight fuse out, I'm back at nominal charging voltage! I finished an hour long ride last night at sunset with a battery that reads 100% charge! So I'm going to ride again today after work to make sure all is the same. And next on to troubleshooting! Is it the Amazon headlight I put in over Christmas break? Is there a short or some issue in the headlight housing? We shall see!

Thank you for the guidance and troubleshooting help. I'll come back to post a summary update of everything, because this bike has never been running better. Also by the way the pickup coil mod is a MIRACULOUS improvement in hot starts! Wow!
 
#15 ·
Alright, at least we know it can put out good charging volts. Now to find the power drain.

So you rode without the headlight and it had good voltage. Does the headlight have a normal amount of brightness when it's on?

Assuming the blue wire mod is done correctly, I suspect the headlight or the wiring to it must be the problem.

Does the high/low beam switch correctly?
 
#21 ·
Yeah, when I had the headlight in the bulb produced great brightness on "low beam" mode. It didn't flicker or anything. It was even brighter on "high beam" mode. So yes, the high/low beam switched correctly. I'm really hoping it's the Amazon headlight bulb...it'll be an easier fix (basically don't use that bulb anymore!) then I can get an awesome LED headlight. I'll look at it this weekend. But it just feels so good to finish a ride with a battery that reads full charge! Thank you.
 
#18 ·
I looked at the link but I didn’t find what the wattage of this bulb is. For sanity you can leave in the fuse and meter across the headlight plug. At least that’ll tell you what voltage is being delivered to the bulb

Here is the bulb I have. I’m real satisfied with it, but I did have to remove/bypass the RLU. Before I did it both the bulb and the high beam dash light flickered. Before you change your bulb it's probably best to pinpoint if it’s the problem or not.

SEALIGHT H4 9003 HB2 LED Motorcycle Headlight Bulb, High/Low Beam, 6000K Xenon White https://www.amazon.com/dp/B071Z7RHY...abc_FNK6REFX7XMA2GQQZFQ1?_encoding=UTF8&psc=1
 
#19 ·
I looked at the link but I didn’t find what the wattage of this bulb is. For sanity you can leave in the fuse and meter across the headlight plug. At least that’ll tell you what voltage is being delivered to the bulb

Here is the bulb I have. I’m real satisfied with it, but I did have to remove/bypass the RLU. Before I did it both the bulb and the high beam dash light flickered. Before you change your bulb it's probably best to pinpoint if it’s the problem or not.

SEALIGHT H4 9003 HB2 LED Motorcycle Headlight Bulb, High/Low Beam, 6000K Xenon White https://www.amazon.com/dp/B071Z7RHY...abc_FNK6REFX7XMA2GQQZFQ1?_encoding=UTF8&psc=1
Wow that LED headlight looks amazing. Was it a simple plug and play installation as far as the locking ring goes? That what it says on the link but I'm checking with you to confirm. But yeah, you are right that first I'll need to nail down the root cause before going down this route.

What do you mean by remove/bypass the RLU?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top