Hi, after spending 3 months searching the internet for various solutions im still having problems on the charging of my GS 500 F (2004 - K5) >.<
the bike was brought about a year ago by myself and the only change needed was a new Reg Rectifier, however 3000 miles later and there was a delightful knock on the engine case signalling the release of the alternator magnets from their housings. a few months, new shells, rotor, tensioner, valves, shims, reg rectifier (AGAIN) and patience later: the bike runs as lovely as it can after such an ordeal but the battery still isnt charging except at around 2000 rpm!

Battery:

New as of FEB 2013

Alternator side:

the alternator is putting out ~68V @ 5000 rpm so it seems to be ok
there is the appropriate resistance (as in infinite) between the coils and the earth
very little res between the terminals of the stator (<0.01 ohm)

Reg Rectifier Side:

sadly i dont have a diode tester so the info is limited but;
the output is about 3-6V at 2-5k Rpm (far too low)

normally i would just say its the Reg Rectifier and be done with it but this will be the 3rd one in the space of a year or so!?

So kindly does anyone have any further ideas of what i can check before i spend the money? (£100 a pop - im reluctant if honest)
Any help would be fantastic!

cheers,
Francis123

I know both local shops around me will test your regulator for you for free...worth asking a place near you. The charging system is pretty simple, and if you are getting enough voltage at the crank, but not enough at the battery, there really aren't too many items between the two. I assume the actual wiring is in good shape, and there isn't anything spliced in there for some reason?

I maybe reading it wrong but if the bike is charging at 2000 Rpm that's doing good. At idol it want show charging.


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Quote from: wolfs02shadow on August 05, 2013, 09:24:22 AM
I maybe reading it wrong but if the bike is charging at 2000 Rpm that's doing good. At idol it want show charging.


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the bike should be putting out at least battery voltage at idle.

OP; if you are sure the battery is good then i would vote R/R as well. are you using oem replacements, or an aftermarket source?

perhaps you could charge the battery externally to a known voltage and plop it back on to see if it was just excessive draw from a low charge? checking voltage with no load won't always show true battery condition. as soon as a load is placed on the battery the voltage may be dropping to less than 5v.

just a few (low cost/free) troubleshooting suggestions. 

thank you for replies guys

will take it along and get a local shop to give it a look over, i think thats the best final move before replacing it. there isnt anything inbetween the points where i took the readings though i think i should have made clear i removed the battery side of the Reg Rect. connection in order to read the output which was 5V on the most recent reading falling to 0V past 2000 rpm (so most likely a miss reading earlier). hence its only charging with an input of 5V at 2000 as its peak.

will take off the battery, take a reading and check once its rigged up again to see if there is any substancial difference

cheers guys, keep them coming

checked the battery off, on and with the bike running; it doesnt drop below 12V but should be reading more than 12V at the terminals when its running, aout 13-14V if memory serves?

Yes, once you are up past idle...anywhere over 2-2500, you should have 13.5-14.5 volts steady.

Quote from: Francis123 on August 05, 2013, 11:15:04 AM
checked the battery off, on and with the bike running; it doesnt drop below 12V but should be reading more than 12V at the terminals when its running, aout 13-14V if memory serves?

I know it seems stupid, but how well is the r/r grounded? a shitty ground connection will cause intermittent/substandard output.

I don't remember on the GS but some bikes ground them through mounting, make sure the mating surfaces are clean and clear of paint/corrosion/dirt.

The RR is grounded through the wiring harness. The 2 pin output does it. The case is not grounded.
The 3 stator input wires are isolated and not grounded to anything.
Next time you replace it, get the MosFet one. It is a better regulator.
Do you have extra accessories on your bike that could be stressing the electrical system?
Is there something that can cause the RR to overheat?
Are you using an appropriate battery?

As I recall, you should have the battery connected to test the RR or at least a small capacitor. I believe the battery serves to help the regulator function. With no load, the output is probably fluctuating and that really confuses a digital meter. (I should look at that on a scope.)

thanks for the tips will take another look tomorrow along with the mechanic's opinion and let you know. will take a look at the MosFet ones, havent heard of them before and have had it up to hear with so called 'genuine parts' only electrical attachment is for heated gloves and this isnt in use most of the time, very rarely if im honest as havent wanted to run the bike with increased load for fear of not making it too far as to overheating i would be very surprised if it was as its bolted on the side behind the side rear pannel so nothing there to cause that from what i can see. Also battery is usual spec in line with service manual

I got the caltric regulator rectifier, it worked very well and still does. Keep in mind that in some occasions, you replace one thing, and the other component in the system goes bad as a result and it's just a never ending circle of replacement that you would have been better off replacing all three at once i.e battery, regulator, and stator.