Alternators - are these the same?

[Paul Fermer]

Hi,

I noticed that my alternator had started to fracture at the back mount and so bought a 2nd hand one off ebay. However, I have come to fit it and by the looks of it the workings of it are different.

This is my existing one:
IMAG0396.jpg


and this is my replacement:
IMAG0398.jpg


Does anyone know why they would be different and should I be okay using it?

I thought I might be able to switch over the back casting but they apear to be very slightly different.

Thanks,

Paul

[V Mad]

The existing one is not original type (Lucas 18ACR) but the second one looks correct.

Your original one looks like a A117.

[Paul Fermer]

Hi Thanks,

Just been having a look at various websites and I think the 43amp Unipart alternator on LD parts looks like my existing one
http://www.ldpart.co.uk/shop/shop.ph...e1f30a96390dbb

So you're right it's not the original fitting. He says this unit provides a battery sensing terminal, which I presume is the single terminal opposite the main three. Well I have a connection in here and there is not one on the replacement one (or the standard alternator) so I assume I can just tape it up without any detriment? what does it do?

[Paul Fermer]

Okay, this 2nd hand purchase is now fitted to the car (and got me to Cranleigh & back) but is reading much higher than before (just under 15V) on the dash voltmeter when driving , yet when idling it's much lower (around 12v). Put a volt meter across the battery and when revving hard it can get to 15V, although tends to sit around 14.8v.

Does this mean the regulator in the alternator is knackered? or is it something else?

Feel I should have just got a new one rather than messing around with 2nd hand parts which are supposedly in good working order – I have said this to myself on several occasions.

Thanks, Paul

[73stagman]

I think the normal regulator cut out for a 12 volt alternator output is around 14.4 volts so your current one sounds like its doing its job!

[V Mad]

!5 volts is a bit high but maybe your meter is slightly over reading. I would feel more xcomfortable with up to 14.5 volts. Second thoughts, if your battery is low, the charge voltage will be a bit high until it recovers.

The reading when idling is misleading as idle speed varies a lot. Rev up to 1000 rpm and it should go higher than 12 volts (with no loads switched on). Is the pulley approx the right size?