Dead alternator .. again?

A dodgy connection can kill the regulator in the alternator. That could likely be the sense wire or battery +ve, battery earth.

Here's a reasonably good link to help understand alternators........

Hmm, all of the connections I can see (battery / earth / alternator etc) all seem pretty clean / solid (no corrosion or looseness etc).

Thanks for that.

FWIW if the thin wire (which is the only wire that to me is even vaguely questionable so far) is for the ignition light and was broken / intermittent would I not have seen the ignition light doing strange things over the last couple of weeks?

All the best ..

T i m

The warning light failing can stop some alternators charging - but that doesn't sound like your fault.

For starters it wouldn't come on :-) Sods law sounds most likely. If you've got a battery charger you can attach it to the large stud & the alternator & chack it behaves similarly to directly across the battery, if not then your wiring's duff.

With ignition switch on but engine not running, touch the thin wire to a good -ve "earth" connection somewhere. If the wiring is ok, the ignition light with come on.

Graham

Thanks for the replies guys.

I'll see what the alternator folk say post test and check / clean / test what else I can while it's away.

All the best ..

T i m

That's what it's most likely to be. Was the same on a Rover I had where the wiring had been chafed through.

We all have our dark secrets ;-)

No secret. I've had a 420, 620, P6, several SD1's...

Well, an update for ya (all). I got the alternator back today tested and NFF?

I re-terminated the warning feed wire (it must have been working for the last two weeks since I replace the alternator as the warning light had been going on and off as/when it should) and fitted it all back in again and it's been fine on a 10 miles test run (with several engine off / on's).

Following Steve B's comments I also checked around all the obvious live / earth terminals and the only one that was a bit 'iffy' was the battery neg to body strap (it was down to about a quarter of the strands at the body end and has now been replaced with a new one). I don't think that was the problem as it was actually connecting and had it had to carry any real current I guess would have simply have fused open?

Anyway, I'll have my fingers crossed for a while ...

All the best ..

T i m

Did you charge the battery before fitting the new alt and firing it up? You can damage alts by attaching a flat-as-a-pancake battery and expecting it to charge it from that point, especially if the alt is already unhappy for some other reason.

Don't be silly.

A new one is unhappy?

Coyoteboy ("Coyoteboy" ) gurgled happily, sounding much like they were saying:

So talk to it nicely.

No I didn't because apart from anything else my fairly new and large battery has one of those 'magic eye' charge indicators and it was green all the time. ;-)

All the best ..

T i m

That's a myth perpetrated by cluless yanks. The alternator will only put out its rated current & that's way more than the battery will draw after a few tens of seconds. & nobodys built a regulator without thermal protection for years anyway.

The depends on the condition of the components in the alt. Bear in mind that alts are not DESIGNED to charge a battery from flat, you're going to be holding it at max current for a good few minutes. If the internals are not up to scratch then that may be enough to stress them over the edge. I've actually had this happen with my celica. The battery was allowed to die for several months and was never charged. When it was put back into use, the battery was charged but had clearly been damaged and was discharging on its own overnight, it would run fine once the alt brought the power back up. After a week or so of this process of /just/ getting the engine to fire and then driving on it the alt packed up. Now this could be coincidence, but it was an aging alt and I believe the strain caused ultimate failure.

Don't be stupid. It's a rare car indeed that doesn't suffer a flat battery at least once in its life. If every time this happened the alternator burnt out there'd be an outcry.

It's a very simple matter to limit the output of the alternator so to a safe amount - after all the output current is already controlled.

Oh - and in the early days of alternators, some cars could exceed the maximum output of the alternator with everything turned on. But they didn't burn out then anymore than now.

Terminating the charging system prematurely by frequently charging a flat battery would have been a more likely occurrence back in the dynamo days.

How do you think the AA and RAC patrol vans cope with doing this week in and week out? They have the additional electrical load of the van's extra equipment, a remote battery pack to charge, and all the customer's flat batteries to boost.

At least as far as the AA is concerned, the vehicle's alternators are bog standard.

Chris

Yes they are.

No worse than turning on the rear window demist & the interior fan at full

It was going to die anyway then. What died on it?