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7V Out Of New Stator At Idle...


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#1 1992TDM850

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Posted 17 September 2020 - 09:55 pm

Hey everyone.  I'm trying to track down a charging problem on my 92 TDM850 and I'm at my wit's end.  When the battery died a couple of months ago, I noticed it was charging low (~12.4V idle, 13.3 volts max), so I replaced the battery and reg/rec.  It killed that reg/rec within a couple of weeks, so I replaced it again and it killed that one too.  I tested the stator and was only seeing 7V AC at idle between each winding and ground, increasing about 7v per 1k RPM.  That seems low to me, but it otherwise it looked good - resistance was infinite between each winding and ground, and within spec between the windings.  I installed a new reg/rec to a place on the bike with better airflow and not mounted to the frame and monitored the reg/rec's temp while the bike idled.  It eventually reached 100C and the voltage dropped - another dead reg/rec.  I finally relented and replaced the stator, but again, 7V AC at idle, climbing about 7v per 1k RPM.  The stator voltages given are at its harness, and I've checked the resistance of the leads from stator to reg/rec and reg/rec to battery and ground, and everything looks good.  

 

I'm still getting about 12.4V at idle and 13.3V WOT, and I'm at a loss.  Anyone have any ideas? 


Edited by 1992TDM850, 17 September 2020 - 09:58 pm.


#2 Bjørge

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Posted 18 September 2020 - 07:47 am

A persistent problem indicates that the root cause is somewhere else. May you have a near-short-circuit, causing excess current draw ? To reveal this, you would need to measure output current with engine running.


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#3 Studley Ramrod

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Posted 18 September 2020 - 08:07 am

:wifgeni:

Hi and welcome.

Never come across a bike burning out so many reg/rec's before.

A faulty/corroded starter solenoid could be causing the low voltage, as could a corroded fusebox.  Are your headlights getting brighter when you rev the engine ?  Mine were getting dimmer when my solenoid was faulty/earthing and the voltage dropped as I revved the engine.  You can test the fusebox for current draw/loss, Haynes manual shows how to do this.


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#4 drewpy

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Posted 18 September 2020 - 11:17 am

those wires from the stator can get soaked in oil and degrade. its only 3 white wires to replace and take it from there


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#5 1992TDM850

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Posted 18 September 2020 - 07:53 pm

Is 7VAC at idle a normal voltage for the stator windings to put out?

 

Because to be clear, that's what I'm seeing between ground and the coil windings.  Nothing else in the circuit.


Edited by 1992TDM850, 18 September 2020 - 07:55 pm.


#6 Bigmatt

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Posted 19 September 2020 - 01:49 am

 

 

Because to be clear, that's what I'm seeing between ground and the coil windings.

Just want to be sure you are checking ac voltage only  between the 3 white wires coming from the stator. Check between wire 1 and 2, then between 2 and 3 then between 3 and 1. It has been a while since I had to check but I think you should be getting somewhere around 50vac when revving up the engine  to 5000 rpms for each pair you check. Here is a link to a fault finding flow chart from Electrex      http://www.oscarmaye.../fault_find.pdf


Edited by Bigmatt, 19 September 2020 - 01:57 am.


#7 fixitsan

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Posted 19 September 2020 - 09:04 am

Just want to be sure you are checking ac voltage only  between the 3 white wires coming from the stator. Check between wire 1 and 2, then between 2 and 3 then between 3 and 1. It has been a while since I had to check but I think you should be getting somewhere around 50vac when revving up the engine  to 5000 rpms for each pair you check. Here is a link to a fault finding flow chart from Electrex      http://www.oscarmaye.../fault_find.pdf

 

 

+1. although it seems like you should measure to ground, the stator is actually completely isolated from ground.

 

Set the meter to AC and as above, measure between pairs of the three wires connecting the stator to the reg/rec.  Anything over 20V at idle, or even a bit less, will still work usually


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#8 butcher650

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Posted 23 September 2020 - 06:37 am

I found with a previous bike that kept killing reg/recs, the only thing that stopped it was a new stator, so sounds like you needed that. 

 

I would follow the advice of the other chaps to what seems to be a continuing issue. Starter solenoids on 3vds are prone to going bad (I've put 2 new ones on my 3vd in my 7 year ownership), but they usually play up by sticking before noticing any voltage issues. 

 

How are your other grounds?  




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