Alternator works?

How to find out if alternator works?
As during starting all dash board turn down, I did borrowed battery charger (CTEK MXS 5.0 Test &Charge) which beside charging can test both battery and alternator. But when I turn engine to 2000 rmp, as in instruction, it show that there is no load from alternator.
Is there any other way how to check alternator before visit service?

Thank you,

Stick a multimeter across the battery terminals. If the voltage doesn't rise when the engine speeds up the alternator isn't charging.

You use a simple VOM (voltmeter) put it on DC volts, put red lead on + and black lead on - on battery posts, run bike rpm up and watch voltage increase. This is more accurate than the dash. If your dash is going blank w/starting it's a sign the batt needs charging.
Pete beat me to it.

Thanks a lot.
Battery is on charger (as informed it is original one - it means 6 years old - I will change it on spring anyhow), Monday I will take multimeter from work and will see.
Thank you once more.

I am confused:
- on idle - 13.3 V
- 2000 rpm - 13.45 V
- 3000 rpm - 13.45 V
- 4000 rpm - 13.46 V
- 5000 rpm - 13.46 V
maybe influence of dying battery, but far from 14.2 - 14.8 V at 5000 rpm.
How you see it, Pete?
Thank you a lot.

That's about right. Dash is never right. You could remove dash connector and clean pins, see if that helps.
Working w/new battery may make a difference too.

This I understand, but it was checked with external voltmeter, not on dash board.

Not sure i understand the problem ? If the alternator isn't working (or is partially not working) surely the battery will just die over time......no matter what you measure it with

If engine will run with lights etc on and voltage isn't dropping then IMHO the alternator is providing at least enough juice for normal loads? My (dash) readout goes all over the shop including waaay down on start up (no wiring fixes and always starts first time), but alternator is fine & dash measured voltage under normal load is in range 13-14 V (never above but moves around)

If I activate ignition (by accident ) when optimate 6 'clever bastard charger' is still connected it freaks out & does same with my wife's golf when on charge (dodgy battery, good alternator) even if I just flick the remote to open doors.....and it won't reset it's mistaken thinking until I switch it OFF-On again......so I wouldn't personally rely on battery charger to tell me my alternators working OK cos it's loaded with complex software that assumes lots of incorrect stuff !

Peter what sort of charger are you using? CTEK MXS 5.0 - yes, oh no. This has a de-sulphurising circuit which in the first instance should never be used on a LiFePO4 battery - from what you are saying, you have the original battery which should be a lead/acid unit. At 6 years old, I'm surprised it still starts your bike!

If you get a replacement battery, make sure you get a charger (though you should not need it for some time) that is appropriate for that battery.

You can start your bike on the battery and once running and warm, disconnect the battery terminal and measure the lead (to the battery) with the multi-meter - this will will tell you the charge voltage form your alternator without the battery interfering. if you bike stops when you remove the +ve lead, you have no alternator output.

From your voltage readings, there may also be others things in play. Firstly, if you have the original earthing point under the starter motor cover, this may be a problem. It is a very poor earthing point. I, as have others, have moved this earthing point to one of the clutch housing bolts pretty much above the original point. This WILL provide a better, more consistent earth. The original earth stud makes a great mounting point for the starter cover...

Secondly, I found on my bike that the cable/plug leading to the 2 main fuses, was not connecting well. Disconnect this plug socket (you will reset your dash and all settings - not a big issue, just have to reset them all later) and see if you can tighten the connectors. These are very similar to the 1/4" quick connect fittings used elsewhere in the automotive world. Using a pair of pliers, slightly crimp the connectors, to tighten them up - re-assemble and go form there. This increased my voltage available by about 0.5 volts!

Thirdly, check your battery terminals for the dreaded green stuff! If you have this, thorough cleaning and reassembly will improve things immensely - use some vaseline to coat the terminals as part of the process - it helps to keep out the green stuff - the green stuff is not a conductor of electricity!

My voltage reads on the dash, around 12.8 - 13.1 volts. At the battery, I get 0.6 - 0.8 volts above this. So at 13 Volts on the dash, I am getting around 132.6 - 13.8 Volts at the battery. My battery is a LiFePO4, and this voltage keeps it at a good charge rate. A lead/acid battery needs around 13.8 Volts to keep it healthy.

Hope this helps (sorry about talking too much, but there is bound to be more to your story)


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The type of connector I am talking about in the second bit above.

As you suggested, after warming I did disconnected battery and engine continues to work. On multimeter it shows about 13.5 V in various rpm. Dash shows about 0.5 V less.
Battery contacts are clean, conservated with vaseline. I will buy new one on spring, the same one I have now (YUASA YTX20CH-BS). For this battery should be CTEK MXS 5.0 charger correct one.
Rest of suggestions make me plan for winter.
But basically I am happy, alternator works!

Winner, now you know the alternator is OK, for sure, Peter.

Generally the difference between the battery voltage and the what is shown on the dash is generally 0.5 - 0.8 Volt. This is rev dependent and also the wiring loom condition. remember we all have these 'talian 'lectrics, and as such, the rule book was thrown out the window a long time ago.

Go ride before the cold weather comes...

hezovka wrote:

Dash shows about 0.5 V less.

I checked my dash against a calibrated multi-meter and got exactly the same 0.5V difference.

It must be a feature!!

In IT systems a permanent bug

tris1948 wrote:

It must be a feature!!

is called a System feature. But this is not such important, just good to know it.

Perhaps I'm a simple man, but I would switch ignition on, tab over to voltmeter function on dash and check voltage, should be 12+/- a bit. Then start the bike. If your alternator is working, it will pop up to 13-14volts. If not, volts will stay the same, maybe drop. If you dont want to trust dash readout, use a volt meter with same points of testing.