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Offline imurray

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Fan affecting charging system
« on: 02 October, 2020, 05:54:10 PM »
Hi folks,

My Mk1 has been off the road for several weeks now with a mechanic about 200 miles from home due to a breakdown. Over the past 12 months I've replaced the stator twice, the reg/rec twice and the battery. It recently broke down again with another charging problem.

At the mechanics, the stator, battery and reg/rec have all been replaced again, it was charging fine and I took it home. Quickly I realised there was still a problem.  It is now back down again with the same mechanic.

The bike is charging fine UNTIL the fan comes on, then it draws power down way too low, down around 11-12 volts or less.

Any suggestions? TIA

Offline Art

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Re: Fan affecting charging system
« Reply #1 on: 02 October, 2020, 07:16:37 PM »
Have I understood this correctly. In the past twelve months you've had 2 stators, 2 regulator/rectifiers and a battery plus another stator, another regulator/rectifier and another battery...

making 3 stators, 3 regulator/rectifiers and 2 batteries in all?

Unbelievable that so many components could fail, fail and fail again, I'd be wanting to know exactly why and would be asking the 'mechanic'...

What was the battery stand by level of charge prior to testing the charging system?
What was the Charging System output voltage at 1,200 RPM?
What was the Charging System output voltage at 5,000 RPM?
What was the exact voltage drop on the electrical load test?
What were the exact symptoms/diagnostics that led to replacing the batteries
What were the exact symptoms/diagnostics that led to replacing the stators
What were the exact symptoms/diagnostics that led to replacing the regulator/rectifier

Did he carry out a voltage drop test between the regulator/rectifier output and the battery terminals? If yes what were the results?

Offline imurray

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Re: Fan affecting charging system
« Reply #2 on: 02 October, 2020, 07:31:27 PM »
Symptoms of stator failure was complete loss of power to dash and subsequently the bike died and couldnt be restarted. Upon inspection, the stator (first time) was visibly burned. 2nd time I didnt see it myself, but failure symptoms were the same and I screwed the battery by repeatedly jump starting it and driving at high revs to try and get to civilisation while touring. Eventually battery failed and I couldnt get any further. Reg / rec was replaced first time, mainly precautionary, but was having charging issues with new stator (no. 2) when using heated grips (low voltage light in grips came on).

Most recently,  battery full (optimate charged). Idle charging I think was around 13 or a bit more. 5000rpm was up over 14v. I drove for about an hour and noticed with a newly fitted voltmeter that charge level was dropping when the bike heated up and went right down below 12.

The bike is currently with a mechanic 200 miles away (recovered by breakdown), so i don't have great control over whats happening, but he admitted today that he can't find the problem and that the bike is fine when cool, but when fan comes on voltage drops.

None of the parts were chinese or ebay, all from reputable UK suppliers and MOSFET.

Offline Art

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Re: Fan affecting charging system
« Reply #3 on: 02 October, 2020, 08:51:51 PM »
The 'complete loss of (electrical) power to dash and subsequently the bike died' is a symptom of a flat battery which may be due to the charging system but not necessarily due to a faulty stator, faulty regulator/rectifier or faulty battery. 'Repeatedly jump starting and riding at high revs' will not kill the battery unless the charging voltage (regulator/rectifier output) exceeds 15v. If any component is suspected of being faulty it should be proved faulty by approved diagnostic testing.

The low voltage light on heated grips are known to come on, its what they do, and is just an indication that for whatever reason the charging system is struggling. It should not be used as part of a diagnosis because it doesn't output anything meaningful. The good news here is that with the battery fully charged (>12.5v and holding charge) and the Charging System outputting more than 13v at 1,200 RPM (idling) and more than 14v at 5,000 RPM you have proved the Charging System (battery, stator and regulator/rectifier) is performing as it should. If there is a fault you need to look elsewhere.

Is the battery of the correct fitment, Yuasa YTZ10S or equivalent 12v 8.6 Ah (10 HR) battery?

Have you checked for standby current drain, if its too high (greater than 0.5 mA) then you could be starting out with a partially flat battery and if you have lights, heated grips, fan running etc the charging system can struggle to keep the battery charged. You may also want to carry out an electrical load voltage test. With the engine running at around 1,500 RPM with all electrics calling for power ideally the battery should have 0.5v more than the initial level of charge prior to testing. If its too much less you can run the test again checking the individual electrical circuits to see where the excessive drain is coming from.

Offline imurray

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Re: Fan affecting charging system
« Reply #4 on: 02 October, 2020, 09:02:31 PM »
*Originally Posted by Art [+]
  if you have lights, heated grips, fan running etc the charging system can struggle to keep the battery charged

Unfortunately, the charging system is struggling to keep the battery charged with just the fan and dipped hesdlight on. Nothing else.

Offline Art

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Re: Fan affecting charging system
« Reply #5 on: 02 October, 2020, 09:06:17 PM »
What are the voltage drop numbers? Have you isolated and tested each circuit separately? What battery do you have fitted?

Offline imurray

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Re: Fan affecting charging system
« Reply #6 on: 02 October, 2020, 09:11:17 PM »
I personally don't currently  have access to the bike. Its with the mechanic chosen by my insurers breakdown recovery. Its a yuasa battery exactly as per your post. As far as I understand, he has checked all connections in charging system and run an independent earth from Reg/Rec to no avail. He has now identified that the stator, battery and reg/rec are all behaving perfectly (and are all brand new), but that the charge voltage drops to 11.3 11.7 when the fan comes on  14+ up to that point.

Offline Art

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Re: Fan affecting charging system
« Reply #7 on: 02 October, 2020, 11:19:46 PM »
Do you suspect that serviceable parts have been replaced willy nilly without having proven them to be faulty? Now an unnecessary ground cable modification where a simple test with a multimeter would have proven the ground cable was good.




Offline imurray

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Re: Fan affecting charging system
« Reply #8 on: 02 October, 2020, 11:24:08 PM »
Its been different mechanics each time. I know for fact (trusted mechanic) stator was gone first time. It was visibly burnt and battery wasn't holding a charge. Reg/rec was precautionary.

I think the current mechanic is unknown to me, but is a main yamaha dealer, so "should" be OK. He just seems to be stumped with diagnosing this.

Offline imurray

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Re: Fan affecting charging system
« Reply #9 on: 02 October, 2020, 11:35:08 PM »
I meant to add, I think this time round it wasn't the charging system at fault, but rather a secondary fault that produced charging symptoms. Just trying to figure out what that fault is not, but seems to be fan related.