Charging voltage drops when engine gets warm

[Nosecone]

'06 AE with 83+K miles (all mine) new fully charged battery with tight connections. The only thing I have done in many months is add the new battery which I keep on an Optimate 3 charger. Datel meter wired directly to the battery terminals. All recalls done. I have Brodie's ignition relay and his ground wiring harness installed. Bike has been flawless until now. Battery voltage reads 13.2 v on the Datel with the ignition off.

On inital engine run after the idle rpm settles at about 1100 the Datel reads 13.6 v. Other readings as follows:

5 bars 14.0 v at 2500 rpm

5 bars 14.0 v at 5000 "

6 bars 14.0 v at 2500 " Note: mid scale is between 5 and 6 bars on the temp gage

7 bars 12.9v at 1100 " idle

7 bars 13.5 v at " " Fans are not on at 7 bars so the engine really is not hot yet

7 bars 13.5 v at 3500 "

7 bars 13.5 v at 5000 " Service manual says a good stator and rectifier/regulator should

produce 14.0 v at 5000 rpm

So when the engine warms up (above midscale) the voltage drops off. Stator and/or rectifier/regulator problem? I am familier with Ionbeam's voltage check for a good stator which I have not done yet. Where is the R/R located? I can't find the location shown in the service manual.

I would think R&R the R/R is an easier first step. If that doesn't solve the prob I'll go after the stator R&R and will have a spare R/R.

What are your thoughts guys?

 

[Fred W]

We've recently just gone through this with another forum member in this thread, though his wasn't heat related.

First thing to do in troubleshooting is to eliminate the MRFWU (Most Recently F***ed With Unit). In other words, try another (ideally know good) battery even though it appears to be fine. If you have one in another bike that you know works fine it it, that is the best.

Next is to check that the Datel isn't lying about your battery voltage.

Then, assuming it is correct, you'll want to measure the output voltage of the Regulator/ Rectifier at the connector by back probing the red and black wires. It should be the same as what you see on the battery within a tenth of a volt or two. If its not then you are getting losses on the harness between the R/R and battery. Do not try and skip steps and do this first because a bad battery can cause the R/R output to look low.

If the R/R output is substandard you'll want to check the stator output using ionbeams info that you mentioned.

If the stator output is good, but the R/R output is low, it could be the R/R, but this is somewhat unlikely.

One of these things will be

 

[Bungie]

This.

My Datel is wired directly to my battery with an inline switch and a DIN connector so that I can remove the panel. The bike nearly always shows 14.2-14.4 volts, but after it's been running for awhile, it will show 13.8 or so. Had me a bit freaked out. Then one day I flipped the unit off and on only to find that when it came back on it was reading 14.2-14.4 volts again. One of the components is introducing some resistance and causing false readings (most likely the switch).

It's been like that for 3 years now. No charging problems.

Next is to check that the Datel isn't lying about your battery voltage.

 

[Nosecone]

Thanks Guys I'll do some checking.

 

[rbentnail]

If I read this correctly: The engine gets hot and the voltage drops?

Uh, no. You went from step A to step C. You skipped step B. The fans should come on. Then the electrical system voltage drops by .5. This is normal, yes? We're talking 1/2 of 1 volt, yes? And not even with an actual troubleshooting-type, good quality electrical meter. Find out why your fans aren't coming on.

Who was it that first said "ride more, stress less"?

 

[JamesK]

By this age/mileage I would suggest that you consider doing the "Stator Wiring Bypass", as originally pioneered by DCarver, and adopted by many Gen 2 owners who've all been suffering from a gradual, but relentless decrease in the charging voltage due to inferior factory wiring b/w the R/R and the Battery.

Some detailed analysis

https://www.fjrforum.com/forum//index.php/topic/146331-krzy8-gen2-charging-circuit/page-4?do=findComment&comment=982204

https://www.fjrforum.com/forum//index.php/topic/146331-krzy8-gen2-charging-circuit/page-5?do=findComment&comment=982549

https://www.fjrforum.com/forum//index.php/topic/146331-krzy8-gen2-charging-circuit/page-5?do=findComment&comment=982549

The Fix - (a big thanks again to Don for all the research)

https://www.fjrforum.com/forum//index.php/topic/146331-krzy8-gen2-charging-circuit/page-8?do=findComment&comment=987156

I've had perfect charging with the Datel consistently sitting on 14.1-14.2 V under most typical loads, very quick recovery after say the fans turn off, etc. I get steady 13.9-14.0V with the Soltek HIDs on at just above idle - I couldn't be happier with the results.

 

[dcarver]

Wow. That was some time ago.

Charging still strong after 1 year and 30k more miles...

 

[Nosecone]

The fans on my FJR don't come on until the temp gets to 8 bars. Even running the rpms to 5000 for a short time the temp would not go above 7 bars and no fans. I ran the same rpm/voltage tests today and got essentually the same results. I run two house fans, one on each side directed at the radiator when I do these engine runs. Temp in the garage was about 90.

During these tests I measured the stator cover temp as high as 208 F with a lasor temp meter when the engine temp gage got to 7 bars. The only additional electrical loads I run are two 30 watt Moto Lites in front that I rarely ever have on (I din't ride at night), the Zumo gps and LED Hiper Lites at the rear. I have used the grip heaters only a few times for brief periods in the seven years I have had the bike. So I doubt that I have stressed the stator's output over the years.

The battery is new and load tests good. Terminals are tight. The voltage seems to drop from 14.0 to about 13.5/13.6 as the engine warms above 6 bars at 5000 rpm. A good rectifier /regulator is supposed to produce 14.0 v at 5000 rpm according to the service manual.

 

[Nosecone]

Well I just got off the phone with the service mgr Dean at Stadium Yamaha. For $40 they will test it and tell me what's wrong. They have done the three valve checks on my AE in the past and have done excellent work for me.

 

[weekend rider]

Your fans do not come on till 8 bars, wow. Mine fans come on between 4 and five bars.. Seems you fan switch might be bad

 

[mcatrophy]

Your fans do not come on till 8 bars, wow. Mine fans come on between 4 and five bars.. Seems you fan switch might be bad

Careful! Yours is a Gen I, his is a Gen II. Twice as many bars on the Gen II, so fans come on at 8 bars not 4.