Car alternator question

huskie69 · Spanner Monkey Joined: 10 Nov 2010 Karma :

The missuses car decided to throw a hissy fit the other day in the middle of nowhere. Wouldn't start up.

I went to her with one of them batteries in a box with jump leads attached to it, and a multimeter.

Battery wasn't being charged so the alternator is fecked. Had to call out the AA - got a free battery out of them which was good. Got the car home on the new battery and dumped the car for later inspection.

Came to remove the alternator today which popped out easily enough. What I'm wondering is when I spin it, should it be generating at least a little bit of leccy? I've stuck the voltmeter on the end, spinning the alternator and absolutely nothing is registering on the voltmeter. I know it's probably shagged but didn't think it would be this shagged. Any ideas?
____________________
'10 Skyjet SJ125-23 - Crashed Sad

> '09 YBR 125 > '53 Suzuki SV650 - Died Sad

> 2010 Suzuki VanVan 125 > '87 Yamaha FZ750 Sold > VTR 1000 FireStorm - Sold > Honda CB1000R

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Probably has a regulator and a rectifier built in. Either of those can die and result in no charge at all.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Raffles · World Chat Champion Joined: 14 Apr 2009 Karma :

Are you spinning it without any wires attached to it? Most car alternators require a live input to excite the rotor.
____________________
A good loser will always be a loser.

huskie69 · Spanner Monkey Joined: 10 Nov 2010 Karma :

Raffles · World Chat Champion Joined: 14 Apr 2009 Karma :

Most alternators don't contain any permanent magnets and will not produce any power without an external live supply. This is why it is usually pointless trying to bump start a vehicle with a completely flat battery.
____________________
A good loser will always be a loser.

flat spot · World Chat Champion Joined: 29 Aug 2003 Karma :

I'm surprised the battery light wasn't showing when it wasn't being charged, afterall that's what it's for. Also just because it wasn't charged doesn't necessarily mean the alternator is knackered. The battery might be knackered and not accepting a charge or a loose or corroded connection could be an issue.

Did you check the voltage coming off the alternator with the car running and the new battery on? If not it's worth a try so you're not throwing money at the wrong problem.

yen_powell · World Chat Champion Joined: 22 Jun 2008 Karma :

I once had a new car that wasn't charging purely because of a broken earth strap. No warning lights on the dash at all.
____________________
Blackmail is a nasty word........but not as nasty as phlegm!
XT1200Z and a DR350 in bits

Cunnington · Spanner Monkey Joined: 01 Jun 2011 Karma :

+1

My mate only finger tightened the bolt securing the body earth onto the gearbox, so the alternator thinks everything is ok as you have 15V between the alternator and engine, but the battery was earthed onto the body so the alternator voltage was floating.

The easy way to check this is a jump lead between the -ve on the battery and the engine block.

And never trust anything your mate does.
____________________
'82 C50, '81 CB100, '84 GS125, '95 NTV650, '00 Bandit 600, '06 SV650, '56 Z1000, '89 NTV600
The Shaggy D.A. wrote: "You are invisible. Those who can see you are trying to kill you."