Suspect Rectifier/Regulator

oKLRider

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Pretty sure mine is shot as I'm only getting 12.24v @5500rpm at the battery, but I'm planning to check it closer tonight. Has anyone had issues there before? 2012 model with ~62k miles.

Thanks,
Luke
 

Nikolajsen

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Never read a post about this here.
But it is a common "problem" an Honda VFR and TransAlp.
 

Dogdaze

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You may want to check the battery too, pretty sure if that is the original one than that is likely culprit. The S10 does suffer from weak battery electrical gremlins.
 

oKLRider

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The battery was my first assumption, but it's only 2 months old. This is actually my third (I think) battery. It died on me yesterday, and was nearly completely depleted. It had to be jumped several times to make it home, and wouldn't stay running at idle speed. My dash lights and gauges even went blank at one point. First time it's given me an issue.
 

eemsreno

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Yamaha has updated the part # on the regulator and that should mean a better part.
Stators are a part that goes bad also.
Oil bath stators will give up sooner or later.
 

Squibb

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Sounds like the stator to me, accepting that by now the RR may also be suspect. Should be reading c14.5v >3000rpm. We really need some AC output readings from the alternator. Your 12.24v at the battery at 5k indicates a constant small discharge in normal riding.

BTW, do check all the neg/earth connections & battery leads first, in case a poor connection is creating a voltage drop. Anything suspicious & you can run a fresh neg lead direct from the battery to any point on the frame/RR to check.
 

Don in Lodi

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A low voltage can go with a high amperage. If the battery should have a shorted cell, the voltage won't read right but the amps would be max'd. A fully charged healthy battery and charging system reads a higher voltage while amps are at a trickle. Just a thought.
 

oKLRider

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Update...

I pulled everything apart, and checked the voltage output from the RR....it's putting out ~15.8v. I also ran an ohm check on the stator connector per the manual, and it's 0.1-0.2, which seems to be in the right range but my multimeter doesn't read as accurate as the specs call for. Considering that the RR is putting out +15v though, the stator should be fine? Also, I checked the ground connection to the engine case, and it's tight.

However, with the battery fully charged (~12.8v) and back in the system, I'm still only getting ~12.2v at the battery at RPM. I've even tried another battery, but same results. I even removed my aux lights from the equation thinking they might causing an issue somehow. No change. Why the drop? What am I missing? Thanks for everyone's suggestions!
 

Squibb

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Whilst you don't give us AC readings from the stator, if I understand correctly the RR is producing 15.8V, when it should be c14.5v DC at 3000rpm.

Then you have a parasitic loss of 3.6v between the RR output & the battery, which seems strange. Have you tried the idea of running a fresh neg/earth lead between the RR & the battery? This will show us whether there is a bad connection somewhere. In the meantime, your RR, the stator & battery are all suspect.

Have you disconnected all retro-fit electricals now? You mention aux lights, but are there any old Satnav cradles, aux plug-ins, intercoms, alarms - ideally they all need disconnecting to check that none are rogue.
 

oKLRider

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Whilst you don't give us AC readings from the stator, if I understand correctly the RR is producing 15.8V, when it should be c14.5v DC at 3000rpm.

Then you have a parasitic loss of 3.6v between the RR output & the battery, which seems strange. Have you tried the idea of running a fresh neg/earth lead between the RR & the battery? This will show us whether there is a bad connection somewhere. In the meantime, your RR, the stator & battery are all suspect.

Have you disconnected all retro-fit electricals now? You mention aux lights, but are there any old Satnav cradles, aux plug-ins, intercoms, alarms - ideally they all need disconnecting to check that none are rogue.
I haven't tried the new ground lead idea, but will do that and report back...along with stator AC output. There are no other additional electrical add-ons, just the aux lights (and associated Skene dimmer), which have been on there for the last ~30k-40k miles.
 

2daMax

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A high electrical load (such as a bad battery, current leakage somewhere in the circuit) can show a lower than 14V at idle RPM. The RR at 15+ V is a concern and could be a cause for killing the battery slowly.

I would check the connections for battery and the starter relay for tightness. The starter relay is near the battery, 2 terminals with High Amp Fuse. Also there is a connector protected by a white translucent plastic covering near the battery, see if there are carbon markings around there. A poor connection at the connectors can generate sparks/archs.
 

oKLRider

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Update...

The starter relay connections are tight, and nothing abnormal.

AC voltage from the stator (at idle). 1st leg: ~2.8v, 2nd leg: ~14.6v, 3rd leg: ~16.7v. Fun fact...with the stator connected disconnected from the RR, I'm getting a weird whine from the stator when I rev it. Plug the stator back in, and the whine goes away. Guessing it has something to do with the difference in electrical load?
 

oKLRider

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Really surprised that it's the stator since I haven't read about other failures, but given my output isn't even across the board that's probably it...no?
 
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oKLRider

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I'll try to pull the side cover tomorrow, and see if anything is burned...or any magic smoke has escaped.
 

Squibb

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Looks like the stator is cooked. We should be looking at >18vac steady at each output lead. What are the Vac readings at 3000rpm (do they stabilize at >70vac) Have you done the resistance readings too?

Then you have the chicken & egg scenario - what caused the probable stator failure. Age, system overload, Reg/rec failure (some go rogue when hot - you are testing cold) or parasitic drain. That voltage drop between RR output & battery terminals still seems strange. BTW, some places have a specialist stator re-wind company in the vicinity - may be worth checking out. Probably some in OC.

Good luck with the fix. Keep us posted.
 
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