Charging system testing guide

[stinkwheel]

Probably been done before but I've just been doing this on my own bike. I have an odd charging fault that only occurrs when thrashing the bike for a prolonged period but the first step is to test the charging system in the garage.

This guide applies to almost all Japanese bikes made from the mid 1970's onwards which have a 12v battery and where you can turn the headlights on without the engine running. It will apply to many other bikes too. If you're not seeing what I'm showing you here, ask, you might have a different setup.

So your bike isn't charging the battery. Step 1 is to check the battery. Charge it and make sure it is holding a charge. Visually check there are no cracks and bulges. If it's an open cell one make sure there is sufficient electrolyte, give it a wipe over with a cloth and clean any corrosion off the battery terminals.

My battery is reasonably new and a good quality one. When charged up it throws the starter over strongly. When I set my multimeter to measure volts DC and measure across the terminals, it reads over 12v and stays there without dropping overnight. Ideally it would be around 13v, mine would be but I've started the bike a few times and run some of the charge out.

If your battery only weakly throws the starter after charging, does not reach 12v or if the voltage drops off overnight, you may well need a new one.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1675_zps3095a52c.jpg

So simple test first. See if the bike is actually putting charge into the battery. Start the bike and run the engine with the voltmeter still attached to the battery set to measure DC volts. You ought to get a rise in voltage to around 14-15volts. If it doesn't rise at all, it's not charging. If it is going higher than this, it's over-charging. You may notice the charging voltage fluctuates up and down with the revs.

Mine is charging at 14v. Looking good so far. If your bike is doing this, the charging system is pretty much doing its job.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1676_zps5d743597.jpg

Now I need to test the alternator. To do this I need to find the regulator/rectifier (reg/rec) which converts the raw electrical output from the alternator into a form fit to charge the battery with. It usually looks something like this. Mine is bolted to the right hand side of the rear subframe.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1677_zps498bfb75.jpg

You now need to identify which wire does what. This will also confirm you definately have the reg/rec if you're unsure by comparing the number and colour of wires to the wiring diagram.

Wiring diagrams look scary but you just need to look at the bits you want. In this case. We are looking for the ALTERNATOR and the REGULATOR/RECTIFIER. I've circled them in red.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/wiring2_zpsa71cea73.png

A closer look shows us three wires leaving the alternator and five wires entering the reg/rec. Some reg/recs have six. Those three wires are connected to the charging coils in the alternator and they run from the alternator to the reg/rec. Check this is definately the case by following the wires, on some 70's bikes, one of them runs through the headlight switch which complicates matters.

So we've found the three charging phase wires, in my case, as with all Hondas of this type, they are all yellow. Other manufacturers use different colours.

Now we need to find the main output wire. This will be one of the remaining 2 or 3 wires on the reg/rec and is connected to either the battery or the starter solenoid. Mine is red and white.

Now find the earth wire. On most wiring diagrams, this will appear to be connected to almost every other componant on the bike. Mine is green.

If you have another wire, this is almost certainly a switched live. You should be able to trace it back to either the fuse box or ignition switch. I don't have one.

https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/wiring3_zps82dfb39c.png

On most bikes, the connection to the reg/rec is via a connector block. Unplug it. VIsually inspect the terminals for damage or corrosion. I've replaced my reg/rec with a different one and so had to use crimp terminals. One of them has been making an intermittant connection and had burned out! This is certainly part of my problem.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1680_zpsa2aee921.jpg

First test is a simple continuity test. Set your multimeter to read volts DC and attach the negative lead to the battery negative. Put the positive lead against the main charging wire and you should read battery voltage.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1683_zpsdc4f847e.jpg

Now put the positive lead against the switched live wire (if fitted). It should read zero with the ignition off and battery voltage with it on.

Now change the setting on the multimeter to read resistance. Test between the earth wire and battery negative. The reading should be zero.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1681_zps28454d62.jpg

Next test is a static test of the charging coils.

WIth your meter still set to measure resistance. Test between each of the charging phase wires in turn and the battery negative. You ought to get an infinately high reading, the same reading as if you hadn't touched anything with the leads.

Now test resistance between each pair of charging phase wires in turn. You should find a low and equal resistance between each pair. In this case 1-2 ohms (my meter doesn't have a more accurate setting). The exact reading is not so important as long as it is a) Low and b) The same for each pair.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1682_zps9b14d8b7.jpg

Last step. Dynamic test of the charging coils.

Set your meter to measure volts AC. Start the engine (it will run off the battery for quite a while). Test between each pair of charging phase wires in turn. You should get a fluctuating voltage between 20 and 90v AC depending on revs.
https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1684_zps18053795.jpg

So what does all this tell us? Here's a few possible faults and what they could mean:

Low/no voltage increase across a known to be good battery when engine runningAlternator fault. Reg/rec fault. Wiring fault. Further testing required.

Excessively high voltage across battery with the engine running Faulty reg/reg. Bad earth connection to reg/rec.

No voltage at main output wire: Broken wire, bad connection to battery or solenoid. Blown main fuse.

No voltage at switched live with ignition on: Broken wire, bad connection to wiring loom.

Open circuit between earth wire and battery negative Broken wire. Bad connection to battery negative terminal. Bad/corroded connection bewteen earth wire and frame-earth. Bad/corroded connection between battery negative and frame earth.

Low resistance between any charging phase wire and battery negative: trapped/worn/chaffed wire shorting to frame between alternator and reg/rec. Short circuit between alternator winding and earth.

High resistance between any pair of charging phase wires: Broken wire between alternator and reg/rec. Broken wire in alternator windings.

Inconsistant resistance between pairs of charging phase wires: Internal short in alternator windings.

No AC voltage between a pair of charging phase wires with engine running: Broken wire in alternator windings. Internal short in alternator windings.

The above list is not exhaustive but in most cases, all of the above tests will check-out normal. That being the case, it is a fairly safe bet the reg/rec unit is faulty as everything else is working as it should be. Reg/recs need special equipment to test properly so most home mechanics test them by excluding other problems.

Looks like my problem is, at least in part, down to a bad connection on one of the charging phases causing damge to the spade terminal. I have replaced the dodgy terminal. I am also fitting a dash-mounted voltmeter so I can keep an eye on it as I think I may als have a more complex problem with heat dissipation from the reg/rec during high speed riding.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Taught2BCauti...]

Excellent post - should be made into a 'sticky'.

It would also be useful when people ask for help with battery or electrical problems, if they could do some basic measurements with a multi-meter and post the following results:

Voltage across the battery terminals when:
1. After the battery has been charged overnight and left standing for 1 hour.
2. The battery is connected back up to the bike, and nothing switched on.
3. Engine running at normal operating temperature, revs at tick-over.
4. Engine running at between 4,000 and 5,000 rpm.
5. After the bike has been left overnight with the battery connected, and nothing switched on.

Even if the readings make little or no sense to them, it will help others to offer more accurate advice.

Also, I have seen some alternator configurations where there is either an additional coil, or one of the three coils is used only when the headlights are running. It is important to know how yours is set-up before taking resistance or AC voltage readings for diagnosis.

Fortunately, there are many good wiring diagrams on the forum.

Take extra care when reading AC voltages with the alternator windings disconnected from the reg/rec, as with high revs and a faulty winding, the output could give a nasty shock!

For example, if all 3 windings are good, you could get readings of 90v, 90v, 90v - but if one of the windings is open circuit, you will get 90v, 90v, 180v - because you are reading the output from the two good coils in series!
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[stinkwheel]

More relevant to my problem than the above but to keep an eye on my problem which I think is an intermittant one, I just fitted a cheap, dash mounting voltmeter to my bike. Just under £3 off ebay.

I've hooked it into the relay I fitted for my heated grips so it comes on with the ignition, brake switch feed would be another place to hook it in at. I've mounted it in the fuse box access panel* using slow setting epoxy. Here I can see it from the riding position but it's not on the dash so it's a) Easy to fit and b) Not a distraction.

https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1686_zps2e9b0a95.jpg
* To the right of the headstock.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[sickpup]

Or what you could do is follow this incredibly easy to follow guide that most people use, that has been referred to many times on this site and completely ignored for a sticky.

Charging fault finder guide.

[stinkwheel]

[a3316534]

As a complete newbie to motorcycle electrics with it often appearing little more than black magic, I find Stinkwheel's guide easier to follow.

[Vincent]

Nice one

I was following it perfectly until the word "electricity" cropped up

I'm pretty useless with electrics, like a lot of other bikers I know.....although I can follow instructions etc.

What size spanner do you use on the Ohm again?

Battery charging problems can be a real bummer as you're always worried something's gonna give while you're out and leave you stranded.

The 800VFR...like wot I've got, is a mother of all electrical problems - Honda really screwed up in the late '90s early '00s it seems

I'd sometimes like to strip the whole bike down and junk most of it.....those skinny little wires too
____________________
Space Is Deep

[stinkwheel]

[Vincent]

I've done the Reg/Rec already...or rather it was done when I got it. Originally the bike had a problem where it would just cut out...usually at speed. The PO couldn't find anyone locally that could fix it and just put up with it. Eventually, thanks to someone online, I found out it was a connector on one of the relays - common fault apparently, esp if the relay becomes disconnected from the frame and get's covered in crud. There's also the same horrible common earth block that the Blackbird has, they pack up. The power, (+), lead from the battery is too thin, the wiring for the lights seems too thin to me and breaks ever-so easily if it isn't routed right...or can move about, same with the ECU wires.
I didn't realise until recently that the clock PCB packs up because the rubber insert get's left out of..... or falls off..... the underside of the nose fairing. I think the holes there to adjust the headlight or similar.
____________________
Space Is Deep

[sickpup]