Lower reading on Volt gauge after fitting new alternator??

My alternator finally gave up the goose the other day, so just fitted a new one.

Started it all up and it seems to work, can turn on all the lights etc etc, start and stop it as much as I want.

However, the volt gauge is now only reading just above red on the low side. It used to sit at just a tick over half way.

I checked the voltage at the big terminal on the alternator and its 11....something.lol. Cant remeber off the top of my head tbh. So that sounds ok to me.

Any ideas?

Im a bit stumped tbh.

Cheers

James

Just checked the voltage across the battery, its sitting at 11.7V. Guessing thats a bit low as im told its meant to be 13.5 to 14 or something. Hmmmm.

Just checked the voltage across the battery, its sitting at 11.7V. Guessing thats a bit low as im told its meant to be 13.5 to 14 or something. Hmmmm.

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Engine running,should see >13.5v on battery.

Yeah, somethings not right. I mean it works and charges and starts it fine.

Just checked, the alternator I removd is an A127/65. The alternator that iv been supplied with is an A133/80. Would that make a huge difference?

it depends on the amps as well so what amp is the new one putting out ??
The tick over voltage should be a lot higher it need to be between 13.6 v olts and 14.4 volts under load with engine running, If you are getting this the i would suspect there is something wrong witht the alternator

hammoj28 said:

it works and charges

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Not if you're getting less than 12V across the battery with the engine running.

Is the pulley a different size or did you re-use the existing one?

Most likely you've not connected the exciter wire up properly, or broken it in the process.

Also possible that the new alternator has a faulty regulator or an internal fault. You'd need to get it tested to find out properly, though.

hammoj28 said:

Just checked, the alternator I removd is an A127/65. The alternator that iv been supplied with is an A133/80. Would that make a huge difference?

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Well it should make a positive difference - not a negative one! That second figure is the ampage, so the one you took off is 65 amp and the new one should be 80 amp. Apart from the fact that it's not working properly, was it a direct replacement?

Shifty1962 said:

Is the pulley a different size or did you re-use the existing one?

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Haven't compared pulley sizes yet, didnt think about that. WIll have a look.

paul_c said:

Most likely you've not connected the exciter wire up properly, or broken it in the process.

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Whats the exciter wire? THe alternator has two wires, the battery one and a thin one which I tohught was the warning light.

instantsquid said:

Well it should make a positive difference - not a negative one! That second figure is the ampage, so the one you took off is 65 amp and the new one should be 80 amp. Apart from the fact that it's not working properly, was it a direct replacement?

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Hmmm, as in direct replacement yes it is. It bolted straight up.

Im guessing I must have a fualt alternator......balls.

Balls indeed

Just out of interest...Why did you change the alernator ? You say it was goosed. Was it noisy as in bearings or not charging ?

I changed it because, it started to sound like a supercharger and got so hot you couldnt even touch it. It was still charging tho. Spoke to a guy who rebuilds them and he says it sounds like the main winding is screwed and it cant be rebuilt...

However, since it was still charging i swapped it back on today and everything works so its got to be the new alternator. Got another on its way.

Cool. Hopefully the next one will be ok.I hate getting new bits that don't work.

Aye your telling me, messes everything up doesnt it.

The bearing behind the fan on the alternator [normaly plain] can get dry,try running a bit of oil down the back of the fan and see if the noise goes away.

Well, went through 3 alternators that didnt work. Moral of the story, dont buy britpart I guess. Seems they have a bad batch at the moment.

Bought a second hand one for 20quid and it works spot on. 14.3 V.

Think the next time im just going to get things rebuilt if I can. Id prefer a rebuilt genuine item than a new cheap item if possible and it'll prob cost the same.