Low charging

Hi, it has been quite a long time since I posted. I have a 2002 SW. A few weeks ago I noticed that the charging system was cutting in and out and the voltage was inconsistent, I could see this as I have a volt meter installed. I checked the rectifier diodes with a multi-meter which all proved to be OK, so that left the regulator part that could be faulty. I did have a non-OEM regulator/rectifier which I had bought to keep as a spare so I decided to replace it. On testing, I found that it was charging around 13-13.5V max, which is approximately 1V less than with the original regulator. This resulted in the battery draining overtime to the point that after 3 days the starting was slow and the engine would not start and flooding made the problem worse because I could not even start it with a jump starter.

OK so now I have to figure out if I have a faulty regulator/rectifier or a faulty stator. I checked the stator with a multi-meter and seems to spec, then I checked for the output AC voltages directly from it and I was getting around 40VAC at about 4000 RPM. I thought it was a bit low so I checked the manual but there is no information of what the voltage should be, I searched this forum and somewhere I read it should be 50VAC+. Can someone please verify what the right voltage should be?

Incidentally according to the manual on the Battery/Charging section (18-6) of the manual it says this:

Check for continuity between each Yellow wire terminal of the alternator side connector and ground.
There should be continuity.


Surely, it should say NO continuity.

Anyway, thanks for anyone that can help regarding my problem.

Hi Yammer.
Maybe a bit of clarity needed over section (18-6 to 18-7) of the manual.
Because of associated circuitry to complete a full test of the charging circuit the Alternator plug P3 needs to be disconnected. (18-6) deals with the stator side of the plug and what readings you should have.
(18-7) deals with the regulator side of the plug and associated readings if you had read further into the section.
So Stator side will read continuities, regulator side they should read open circuits.

Hope this helps.

Be safe, be seen!

JohnyC wrote:

Hi Yammer.
Maybe a bit of clarity needed over section (18-6 to 18-7) of the manual.
Because of associated circuitry to complete a full test of the charging circuit the Alternator plug P3 needs to be disconnected. (18-6) deals with the stator side of the plug and what readings you should have.
(18-7) deals with the regulator side of the plug and associated readings if you had read further into the section.
So Stator side will read continuities, regulator side they should read open circuits.

Hope this helps.

Be safe, be seen!

Hi JohnyC,

Thank you for the reply. The reason I quoted what the section in 18-6 said, is because it is totally wrong. The instructions given in the manual can be a little confusing because in the next paragraph it does say to replace the alternator stater if the resistance is out of spec or if any wire has continuity to the ground.

I checked the stator again today and inserted 3 sliders in the plug so that I can connect crocodile clips from the test leads of my multimeter to get a better stable reading. It is up to spec, .1 ohms on all 3 coils and 50vac at 5000 rpm. So the problem is definately the regulator/rectifier.

It wouldn't be the first time that an error has been detected in the service manual. Well done on your diagnosis and please keep us informed of your progress.

Hello again, sorry for the late update but I actually replaced the voltage regulator/rectifier only a week ago because my wing has been sitting in the garage for the last 3 months. I took another chance and bought another non-OEM regulator/rectifier off ebay because I did not fancy paying €205.40 that was quoted from my local Honda agent (apart from not having it in stock) only to find I still have the problem. Anyway, it worked as it should but I have to point out a problem that I did not think was effecting anything. It was the idle setting. It was just above 1000 rpm and although the scooter worked fine otherwise the battery was not getting charged while idle, so if I come to a red light, the battery voltage was barely over 12v indicating that it was not getting any charge during this time or if it was, it was minimal. Once I increased the RPM to 1,400 (specs does say 1,300 RPM +-100) the voltage went up to 14.6v.

Although it may not have any apparent issue if you have a healthy battery, if you ride in congested traffic and you have to stop at lengthy traffic lights it may impact the life of your battery. I do have a volt meter on the dash and have been noticing the dropped voltage on idle ever since I had it installed and it always bothered me, but I never thought the problem was the low idle speed.

Hi Yammer.

I do apologise, I thought I had mentioned to check the tick-over speed when checking voltage outputs in my post.
Well spotted anyway!

Be safe, be seen!

Whenever I check voltage I am always concerned with the maximum voltage at the RPM given by the specs which is where normal riding would normally be, but tick-over speed as in my case which was below spec is important too.