What voltage direct from Alternator

[Hobbes_imp]

Hi, I have a charging problem, it's actually on a CB900 but I'm thinking that the charging systems will be pretty similar.
All the yellow wires from the generator check out as per manual specs, black and white wires also fine, but only getting 14.5 volts A/C out of each wire when using AC volt meter between single yellow and ground. No volts coming from Reg/Rec so thought that was faulty, I've replaced it with a new one and still the same results.
I always thought that un regulated you get about 30 volts AC from the generator
Thanks for any input

 

[Lord Popgun]

The service manual does not list the alternator output AC values, just resistance measurements. The Common service manual goes into detail of how Honda's alternator types and voltage rectifier/regulators work, no values are givin for just alternator output.

And thats about all I can help with.

 

[CBXBob_imp]

Hi, I have a charging problem, it's actually on a CB900 but I'm thinking that the charging systems will be pretty similar.
All the yellow wires from the generator check out as per manual specs, black and white wires also fine, but only getting 14.5 volts A/C out of each wire when using AC volt meter between single yellow and ground. No volts coming from Reg/Rec so thought that was faulty, I've replaced it with a new one and still the same results.
I always thought that un regulated you get about 30 volts AC from the generator
Thanks for any input

The AC voltage is checked between the yellow wires and is around 28 to 30 volts,if I remember correctly.

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[CIP57_imp]

It's 28 V or 336 watts Went through this info for heated gear

 

[Hobbes_imp]

Thanks, thought it was up around there, according to the info in the Clymer manual all the windings check out with the correct resistance and no earths so what would cause the low alternator output.

 

[JohnNevets_imp]

I'll be honest. I don't know how this is supposed to be measured, but you said you measured it to ground. CBXbob said that the 28 volts, was measured between the yellow wires. I just want to make sure it's not something stupid like that. I don't know how these were wired but is one of the yellows acting like a household neutral?

 

[CIP57_imp]

Hobbes,

Assuming you have a charged battery so there's no false reading, you should be getting out of the rectifier at the battery 14.2-14.6V at 5000 RPM's. You have replaced the the regulator/rectifier and i assume checked the main 30amp fuse going to the battery from the rectifier. The only ground between the stator and battery is at the battery negative. It seems like the stator could be bad.

 

[vfrpaul98_imp]

I'll be honest. I don't know how this is supposed to be measured, but you said you measured it to ground. CBXbob said that the 28 volts, was measured between the yellow wires. I just want to make sure it's not something stupid like that. I don't know how these were wired but is one of the yellows acting like a household neutral?

no neutral, your three yellow wires from the alt are windings. picture a triangle with one yellow wire attached to each of the triangles points and the flat sides of the triangle are the three windings. the north and south poles of the magnets contained in the rotor spinning inside the stator windings create the ac current pulses sent to the reg/rectifier. if ac voltage is measured between the yellow wires you will see consistant ac voltage from all three between them selves. if you measure from one yellow wire and the other to ground you will see only half of the spec voltage because the ground is not a generating component. so 28 vac between the yellow wires and 14 v ac/dc from one yellow wire and the other meter lead to ground.
Paul

 

[JohnNevets_imp]

Thanks for the explanation. So unless I missed something (a good possibility) Hobbes generator is working correctly, right? He said it was measuring 14.5 volts to ground so the alternator/ generator is working correctly. So it is probably something past this point in the circuit? I'm trying to clarify this for my self as much as Hobbes.

 

[vfrpaul98_imp]

Thanks for the explanation. So unless I missed something (a good possibility) Hobbes generator is working correctly, right? He said it was measuring 14.5 volts to ground so the alternator/ generator is working correctly. So it is probably something past this point in the circuit? I'm trying to clarify this for my self as much as Hobbes.

yes measure ac volts between the yellow wires from the stator, do not measure from yellow stator wires to ground.
to check wire circuit, engine stopped, keyswitch off, battery cables connected . go to the reg/rectifier in front of the rear tire, disconnect the black harness connector that contains the red and green wires. measure the red wire + to the green wire- at the harness for battery voltage. if o.k. the wire circuit should be good. if no battery voltage check the red wire from the harness connector to the + battery post circuit include the 30 amp fuse in the starter relay switch for continuity.. also check from the green wire at the harness connector to the - battery post for continuity. good luck.
Paul

 

[Hobbes_imp]

Hi, thanks for all the input, I've done some more checks and results as follows
Alternator yellow wires, all continuity tests as per book
Voltage from yellow wires to earth all 14 to 15 volts AC
Voltage from yellow wires to each other, only about 7 or 8 volts AC
Red/White from harness to Green from harness into Reg/rec 12.9 volts, full battery voltage
With fused link removed and ammeter fused in its place I get negative 8 amps when ignition first switched on, when running the ammeter goes to zero or + 2 amps max
Looking at the head light when running there is a little brightening of the light as you go off tickover but then it goes back to how it was before starting the engine
Thanks again