Alternator does not devolep any voltage.

The guys in automotive will probably grab hold of this and give you many options.

My guess is that there is an open circuit (or broken lead) in the return path from the battery system to the excitation field in the alternator an dwith no excitation field there is no voltage produced.

When you had it on the test bed and applied voltage, you "kick started" the excitation field and from your description it works.

This suggests the fault is in the wiring. Since the machine has worked in the past, there is probably damage.

It is broken...

Dear Sir,

The alternator under question may be having excitation problem, and it may be due to some where loose connection in the circuit.

In fact I am also very much interested in knowing the exact reason from the learned experts.

So pl. do keep me informed .

Regards,

Ulhas Pradhan

Codey, I think if it works on the test bench it must be a fault in the wiring, don't you think?

Hello Electroman - possibly, but I wasn't quite sure what happened on the test bench. E.g. where did he put the external 24volt? Did it produce rated current output? (assuming the test bench has enough power and speed) Perhaps the 24volt was put on the warning lamp connection, and the problem is blown bulb. Incidentally, once the alternator is charging you can of course remove the bulb and it continues to charge OK.

Cheers....Codey

A well worded and reply full of pertinent information.

A good answer for you.

Was it working properly when you gave it a kick start or was it hesitant, like you now, not knowing what's the problem.

If the generator produced plenty of juice straight away 'when you kick start it' then the brushes must be, OK. (It is quite common that they tend to wear after a while and cause intermittent contact problems.)

If the brushes are all right then you should have checked the output from the regulator to make sure you're getting enough output current (not just voltage) enough to excite the rotor coil to sufficient level.

And do not forget to further back trace the regulator circuit to make sure that the regulator is getting power also because that is equally important too, you know!

What I'm getting at is - sometimes there's an innocent little device called FUSE that might be in the path of the exciter circuit, you with me?

These a the basics should be checked before you start to dismantle the whole machine and later make yourself embarrassed. You can check it with the operator but do not trust him, check it yourself!

cheers,

check for excitation this might come through a bulb filament on some machine so if bulb is blown alternator will not charge

All good responses so far.

The reason that I suggested "outside" the alternator is that the OP indicated they started the machine with alternator and all else in place, but that seems to have depleted the battery.

Thus, the battery was providing enough voltage that should have energised the excitation coils in the alternator if that potential was getting back to the alternator.

Check whether the replacement alternator in the machine is working. That will give indication as to whether the fault lies in the machine or the alternator.

rpm indicator most likely would be an a.c signal, battery charger a heavy gauge wire and the one you could not confirm the excitation wire.why dont you try self excitation with machine running loop battery charger wire with the one you could not confirm by touching them for a second or two and check to see if alternator starts charging and work your way back to the fuse panel or igniton switch etc.you might want to extend the test wires out of machine engine compartment to do so

dear Batzee

every alternator field winding have its own residual flux (magnatisation).due to this residual flux witouht appliy any excitation voltage , residual voltage must be built up and it is arround 10% of nominal voltage . but due to a long stop of alterantor ,it lost its residual flux (magnatisation).to over come this problem field flashing is required to regain residual flux (magnatisation) and it can be achive by appling low voltage DC (12 V to 24 V Dc). in your case you has also applied 24 volt DC,means you performe field flashing on your machine and get residual magnatisation.

regards

suresh kumar paliwal

No, that's not right. What you say is correct for a dynamo but not alternator. See #4. With alternator there's no need to magnetise the field by flashing etc as the current to the charge warning lamp does it. And if you tried it it wouldn't work, it wouldn't hold the magnetism.

A dynamo needs to be magnetised when new (perhaps done in the factory) or if it needs to be repolarised as it charges -ve when +ve is needed or vice-versa. Some early alternators could be reversed, but not like a dynamo, you had to alter the internal wiring. I'm not aware of any modern ones where this is possible, it's -ve ground and that's it.

Cheers........Codey