Alternator issues

[S4_dan]

Hey guys,

Fitted a 2nd hand alternator just now to the Audi and fired it up, the battery light went out on the dash. There was a whining noise from the engine so I went to try and source it and could smell burning. It was the alternator making the whine.

The battery gauge was reading 13v and went to 14.5v when I revved it. I went to other car to get a voltmeter and when I returned the gauge was showing just under 12v. I went to the alternator and I could smell it was getting hot! I turned the car off promptly.

Any ideas on what could causing the alternator to get hot? I appreciate it could of been a faulty alternator to start with but I just want to try and rule everything out before spending more money on another alternator.

Cheers,

Dan

 

[S4_dan]

Does anyone have a wiring diagram of the Batt+ lead from the alternator on the 1.8 ADR engine please?
Or do you know if it runs direct to the battery from the Alt, or does it go to the started motor?

Any ideas on where the engine earth strap is located?

Cheers,

Dan

 

[aragorn]

Is the battery flat? The alternator will get hot if its under load, ie charging a very flat battery.

It could also get hot if theres some sort of short circuit.

The b+ lead runs from the alternator, down round the back of the engine and connects to the big terminal on the starter motor.

The main battery feed then runs from the starter motor up to the battery itself.

If that main battery cable was shorting somewhere you'd know about it, as it'd be on fire

Engine earth strap is located on the drivers side engine mounting bracket.

If the engine starts fine, the earthstrap must be ok, as starting current is far higher than charging current...

 

[S4_dan]

Hmmm,

The battery wasn't flat. It was showing 12v and cranked the car over fine to start with. The gauge was up and down when revving the engine, then 5 mins later the alternator was smelling and no longer charging.

I thought maybe a bad earth or a dodgy batt+ lead and thus leading to a large current draw from the alternator. I've ordered a new regulator which will be here tomorrow and I'll fit that onto the original alternator and try that again.

I'll also check the lead to the starter just to be double sure.

So it could be likely that it was the replacement alternator that was faulty.

Cheers Kev, a wealth of knowledge!

Dan