24v Alternator charging/fault issue

[Wood wasp]

I had charge light come on few weeks ago and put volt meter onto alternator - not charging. Took it off to get repaired and after a lot of checks the repair company finally found the windings were faulty (a fault than only became apparent when it was under load).

 

They changed windings and tested it on their rig and all good, I fitted it to machine today... Not charging. Is it possible for me to have a fault or short in wiring that is overloading and burning out the windings almost instantaneously? The repair company are going to phone me tomorrow with their thoughts, I also have a spare alternator I can fit in meantime but reluctant to do so in case I do have a fault somewhere else and knacker it also.

 

Thanks in advance for any info

[gensetsteve]

I had charge light come on few weeks ago and put volt meter onto alternator - not charging. Took it off to get repaired and after a lot of checks the repair company finally found the windings were faulty (a fault than only became apparent when it was under load).

 

They changed windings and tested it on their rig and all good, I fitted it to machine today... Not charging. Is it possible for me to have a fault or short in wiring that is overloading and burning out the windings almost instantaneously? The repair company are going to phone me tomorrow with their thoughts, I also have a spare alternator I can fit in meantime but reluctant to do so in case I do have a fault somewhere else and knacker it also.

 

Thanks in advance for any info

 

To get the charge alternator to charge you need to excite it with 24 volts. The small wire often a spade terminal gets its feed from the ignition switch so there could be a fault on this circuit. To test alternators on site we pull the wire off and jump it of the battery. If we still don't get an out put its the alternator.

[Craig.]

When you reconnected the battery, or the wires if working live, did you get a spark? Most times when connecting the battery you will get a tiny spark/ crackle from things drawing current, interior light, radio, volt dropper, tacho if wagon, but a noticeable spark would point to a current draw, if nothing is on, there is a good chance of a fault.

[Wood wasp]

Ok thanks Steve. I should've said I put meter onto main alternator output and charge light output, nothing from charge pin and only 23.6v from main output.

 

Is it possible to have a short with that can "burn out" an alternator?

[Wood wasp]

Ok thanks Steve. I should've said I put meter onto main alternator output and charge light output, nothing from charge pin and only 23.6v from main output.

 

Is it possible to have a short with that can "burn out" an alternator?

 

 

I've not had batteries off Craig, just the alternator as when light first came on I put meter on alternator terminals and was only 23v

[Craig.]

Ok thanks Steve. I should've said I put meter onto main alternator output and charge light output, nothing from charge pin and only 23.6v from main output.

 

Is it possible to have a short with that can "burn out" an alternator?

 

Did you check the voltage on the charge light wire from the machine? you need power on that to start the alternator charging.

The charge light earths through the alternator, via the small terminal.

Once the alternator charge voltage equals the battery voltage the light goes out, as the light cant earth through the alternator.

[Wood wasp]

Yes the charge wire was still connected to charge pin on alternator when I tested it. The charge light came on when I slid off a stump and machine received quite a jolt. I could swap alternators to see if fault def in alternator or in wiring elsewhere, just concerned that if is wiring awry then I may cook another alternator.. If this possible.

[Craig.]

Unless the is a short in the harness, it is unlikely to burn out the alternator. To check if you've got a short, make sure all electrics are turned off, disconnect the battery negative terminal and put a test lamp between the battery negative and the terminal on the lead or chassis, and give the harness a good shake and a bit of a pull and pushing, watching the lamp to see if its lights. Light equals a short, the area of the harness you where moving when the light comes on is a good place to look for a fault.

[Wood wasp]

Ok will do thanks. It's fairly old forestry machine and it's not unknown in these machines for a sudden jolt to mean wires get nipped against cab or chassis. I'll try find time over weekend to investigate a bit, thanks again for your time