Alternator woes.

[Nigelw]

Helping a good friend who is caravaning in Europe this season and he fitted a new alternator 6weeks ago and had done roughly 2000miles on it.

He said it as driving along happily and then out of nowhere the alternator started howling and there was a burning smell acompanied by the charge light on the dash, rescued by ADAC and taken to a campsite close by to be repaired, had another brand new alternator shipped from the UK and fitted it, less than 25miles driving and the same thing happened again.

I went over to help them with a dodgy starter motor and to look over the alternator and checked the alternator output and it was barely 1.1V and howling like a banshee.

Incidentally when swapping the starter over the power feed terminal sheared off when going to undo the terminal, there seemed to be very little connection if this makes any difference I really don't know.

Have sourced a known good one from a forum friend in Hoegarden to get and try and sort them out but not wanting to fit the new second hand alternator only for the same to happen again.

any ideas?

[Puffernutter]

Too tight drive belt trashing the bearings? Alignment issue - alternator mounting skewing the drive? Alternator to small load wouldn't be an issue, if you were pulling huge numbers of amps,that may cause a problem.

Peter

[Puffernutter]

Too tight drive belt trashing the bearings? Alignment issue - alternator mounting skewing the drive? Alternator to small load wouldn't be an issue, if you were pulling huge numbers of amps,that may cause a problem.

Peter

[Nigelw]

I checked drive belt tension and it was true, belt was if anything a tad slack for me personally.

forgot to mention it's a 4.2 LSE, it has an abundance of electricals as standard.

Both alternators failed in the exact same way just one covered 2000 miles and the replacement a mere 25 before failing.

[elbekko]

Dodgy battery drawing too much power?

Also, next time you're in Hoegaarden, come say hi!

[David Sparkes]

Picking up on your comment "Incidentally when swapping the starter over the power feed terminal sheared off when going to undo the terminal, there seemed to be very little connection if this makes any difference I really don't know.".

What is the physical path of the alternator output to the battery?

If this path is mechanically broken in any way, perhaps by a faulty connection at an intermediate point, like a starter motor terminal, the alternator output will not be regulated, the voltage will go very high (say greater than 16 volts), and the alternator will start to fail, most likely the diodes. The howling will be caused by the uneven electro-mechanical loading inside the alternator, as only one or two of the output windings are actually producing any power.

It is perhaps worth a reminder, that the electrical energy is produced mechanically. While all three output windings are working properly the load on the drive belt is constant, when one of the output windings fails (or its associated diodes fails), the load on the drive belt pulses, rapidly. It is this rapid variation in load which causes the drive belt to howl.

Remember also that a weak mechanical / electrical connection may work satisfactorily while the electrical load is small, but is likely to fail as the electrical load increases, or as the small load is maintained for some time.

HTH