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Discussion Starter #1
This may be a longer post, but I want to give you all the information I can to perhaps resolve this issue. I know there are a lot of smarter people than me out there.

I have a 2003 VN750 which I personally have chopped and bobbed; however, the heart of the bike is still there. I purchased the doner bike with a known bad stator. Since then, I have completed the following.

1. Pulled engine and replaced stator...along with the tuxedo modification. Replaced the rotor which was scarred up from stator failure. Like a dumbass, I did not go with the best stator available. It is an Electrosport if it makes any difference.

2. Replaced ignition switch from Handlebar area and went with a simple on-off-accessory key style.

3. Has a NEW Shorai Lithium Battery

4. has a NEW Mosfet Voltage regulator and wiring harness.

5. Has LED Turn signals. Has single bobber tailight. I already bypassed the headlight relay by moving blue wire.

6. This bike no longer has the instrument cluster. It is as simple as a bobber can ge.

The bike runs fantastic at 12 volts and full charge when its cold. After it heats up, it starts to act up and finally quits all together. Today, it killed the battery in a short time....ANF it blew the 30amp fuse for some reason. Never done that before.

Stator is testing good....I think. Getting 50-60 AC Volts through each leg of stator leads. Also, each leg is zero ing out on the ohm meter. However, I am still only getting 12.6-12.8 volts from this new mosfet voltage regulator at any speed. Then, all of a sudden, the bottom will drop out of the battery and voltage will be sucked out of it. Next thing I know, the brand new battery is dead. I even pulled the headlight and tail light fuse to see if it made a difference...no change.

I guess my question is: Is is still possible the stator is acting up even if it is testing good with a meter? Could it be shorting out when it gets hot? Any other ideas?

I am planning on giving my new build to my son who is currently deployed in the US Army overseas. I have about two months to work this out. He has spent the past 6 years protecting me here in the USA, it is the least I can do or him as a surprise when he comes home. I just need to work through this issue.
 

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Yes, the stator can short to ground after it warms up, best to test hot and cold.

The Two Wire mod might help if the stator can pass the hot test. (pinned post in the Electrical section)
 

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Discussion Starter #3
Interesting

Mr Spockster,
My start button will go dead and I had assumed that it was because the battery was low, however; tonight it still did not work with a fresh battery. I may try this....very interesting.

Could it really be this simple? My luck does not generally run this way.
 

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Ric-Flair,

I've been looking over the electrical schematic, and have some details that might help you track down your problem.

The only way the main fuse can blow is if the stator is charging the battery via the R/R at more than 30 amps (virtually impossible), or if the battery is discharging at 30 amps, which will only happen if there is a short.

If the stator shorts to ground the main fuse would not blow, since the battery can't discharge backwards through the rectifier to the stator (diodes are preventing that from happening).

So, that basically leaves a short somewhere other than the stator. (though you might as well test the stator hot like spockster recommends just to cover all bases)

Spockster's recommendation to try the two-wire mod is a natural place to start, since you say your start button is flaky. A short in the starter relay in the junction box would certainly drain the battery, even with a good stator, possibly badly enough to blow the fuse.

If the two-wire mod doesn't give you a good fix, or fixes your starting issues but not your power loss-when-hot issues, then the problem might be with the FAN switch and/or relay. If there's something wonky with the fan relay such that it shorts out when the bike heats up and trips the thermostat, that sort of describes your situation, loss of all electrical when the bike gets warmed up. Unfortunately a bad fan relay is hard to isolate from the rest of the circuitry since it shares a junction box pin with the rectifier's supply voltage, so rule out everything else first.
 

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Mr Spockster,
My start button will go dead and I had assumed that it was because the battery was low, however; tonight it still did not work with a fresh battery. I may try this....very interesting.

Could it really be this simple? My luck does not generally run this way.
Hope the fix is that simple! The mod did fix charging problems on at least two bikes with TPE stators and MOSFET R/Rs.

A couple of ways to try the Two Wire mod ...

Release the wires from the connector and tie them together away from the connector.

-or-

Cut the wires at the connector, leaving enough to splice back on if needed, splice the two wires together away from the connector.

If the Junction Box is causing the problem in that particular circuit, it will work.

If the mod doesn't help, the problem may be elsewhere in the JB or harness, as Thorn has outlined.
 

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there is a 3rd way as well

leave the wires on the connector, and splice between them. Thats how mine is done.
True, that will make the start button work, but it doesn't isolate the problem circuit/relay in the JB.
 

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Discussion Starter #8
On Second Thought

The more I think about it, the more I am going to go through some of my work a little more.

I replaced the key switch mounted on the handlebars with a simple three position key switch (on-off-accessory) Of course, wires had to be grouped and attached onto certain key switch positions (schematics and info I obtained here on this website...SlimVulcanRider I think) anyway, I am wondering if perhaps one of these connections could be shorting out.

ALso,

I did wire the fan onto a manual toggle switch. However, I am not sure just where I am drawing the power from...just a hot lead probably. I may go back and remove the tank, and cut the wire loose. I could run a fused wire directly to the battery pretty easily. This would take the fan off the bike's wiring all together. The more I think about it, something could be shorting and drawing the battery down...and this would also explain the blown 30amp main fuse too, right?

Feeling a little better about this...hopefully I will figure this out. My son is due back in the US on September 30th. I need to be ready for him. I dream of giving the bike to him the day he returns from overseas. #Ranger #GoArmy #Infantry
 

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If you've already got the fan on a manual switch, pull the wires off of junction box pins 4 and 5 (black/yellow, blue wires on ten pin connector). That'll remove any path to ground from the potentially faulty fan relay or cooling fan switch/thermostat. Rule out as many variables as possible when chasing gremlins.

Since you're dealing with a short that is shunting enough current to blow the 30 amp main, I'd be cautious about wiring anything directly to the battery. That fuse prevented a disaster, and you don't know if its the fan motor that did it or not. Wherever you've wired your manual switch in, leave it there for now. Either it's not causing any problems, or it IS causing problems and the fuse box is saving your bacon!

It would be good from a diagnostic standpoint to know which wire you spliced into, though, so if you find it, post it. :)
 

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Discussion Starter #10
Very helpful advice Mr. Thorn. I will indeed pull the wires from the 10 pin connector. I am so stupid sometimes.

If I ran a new wire FROM the battery....through an inline fuse link ...to the toggle switch....then to the fan...that would be safe, correct? The fan is just grounded to the frame.

I too am anxious to see just what wire I used to power the fan. Like i said before...the bike runs fantastic, but these electrical gremlins are popping up now. Thinking about putting a toggle on the aftermarket headlight ground wire too. I just want to eliminate any extra draw on the battery that I absolutely do not need. Florida does not require a headlight to be on during the day. Any negatives?
 

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Yeah, if you've got an inline fuse, you're set. Sorry I missed that aspect of your original comment.

If law doesn't require a headlight, there's no negative to ripping out quite a bit of electrical stuff.

If you do the blue wire mod and the RLU bypass mod that gets you fused power to the headlight when the ignition is 'on' and 100% manual control over the headlight filaments using the headlight dimmer switch. You can also disconnect the yellow wire from the stator to the junction box as part of the blue wire mod. Adding in a shutoff switch near the existing dimmer switch should be easier than running all new wire to the headlight.

Any reason you would put the toggle switch on the ground wire instead of the hot wire? Seems like the closer the switch is to the 'source' the better off you are if there's ever a short in the system.

On a vaguely related note, I once had my brother-in-law tell me he'd replaced a light fixture in his house. Knowing he isn't the handiest person I jokingly said "hope you shut off the breaker". He said "Naw, I just shut off the light switch. He's lucky the electrician switched the hot wire instead of the neutral wire on that particular fixture.
 

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The battery falling out all of a sudden is just a side effect of running LiPo. Unlike NiCad they do not slowly discharge. They hold full voltage all the way until the low cutoff sensor kills the output to protect the battery, as a LiPo that goes below the threshold voltage is destroyed. If you had a NiCad or lead acid in there you'd see different symptoms of the bike such as hard starting and excessive backfiring when the voltage got low to give you a warning when it begins to drop.

All we do know is that the battery is not charging, or discharging rapidly at a rate faster than the stator is charging. Likely the discharge, since the fuse blew. Use an amp meter (like a clamp) to determine where the amperage is being drawn from using targeted pinpoints in the electrical starting at the source voltage and working backwards.
 

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If you're wiring the fan direct, won't you need a relay?

One of those $5 relays from the auto store would do, have one on my truck fan. Until I put the relay on it, it kept burning out the adjustable temp switch.

The 12v wire to your fan may get warm without a relay.
 

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If you're wiring the fan direct, won't you need a relay?
Not if he is using the stock relay (still as yet to do the mod), fan is a negative trigger. My bike has a switch inline that goes to ground so I can turn my fan on early in traffic. On a modded setup he needs a single pole single throw relay (SPST).
 

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a heavy enough switch would work without the relay as well. the fan is fused at what? 10 amp? any switch with a higher current rating should be just fine without a relay.

I would however, replace all the wiring with fresh, heavier gauge that what is in the harness if I were to do a fan switch
 

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Not if he is using the stock relay .
He said he wanted to bypass the harness and JB, I think.

I recall the fan wires being larger, I may be wrong. Too many fans lately.
 

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a heavy enough switch would work without the relay as well. the fan is fused at what? 10 amp? any switch with a higher current rating should be just fine without a relay.

I would however, replace all the wiring with fresh, heavier gauge that what is in the harness if I were to do a fan switch
The arching inside that switch at that current would burn it up pretty quickly with carbon and pitting. The fan would need to be turned on and off too many times for that application at that current those heavy throw switches only work when you only have to do it every once in awhile
 

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Discussion Starter #19
Mainly because the aftermarket headlight has two power leads for high beam and dual beam. I thought a single toggle on a ground would work to control both beams....no other reason other than that.

When I give this bike to my son...I want it to be pretty bulletproof. He never really knows what the maintenance situation will be wherever he is based. Like I said...this bobber is really pretty minimal...but its very cool I think. I hope he will like it. Afterall, he sort of had an input of what was cool when I was building this thing...but he has zero idea that I am giving him the bike when he returns from his 4th deployment.

This little 750 has fought me the entire way. I previously bobbed a Honda 750 Ace without nearly as many issues as this bike is giving me; however, this VN750 will run circles around the Honda. I feel like this build is very near complete, I just have to beat these demons. Once I figure out how to post photos on this site, I will show you guys what is going on.

#Army #GoArmyBeatNavy #Warrior
 
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