Is the alternator fault 15.1v out.

[nickjaxe]

Hi all my brother in law asked me to look at his cars batt as the cars low batt volts warning came on.

Its a 2009/10 Astra 1.6 petrol.

Looks like its has the original GM batt from 2009....car was 2 years old when he bought it and has never changed the batt.

I put my multi tester volt meter on the batt....no load 12.6v....with the head lamps on engine off drops to 11.6v....dont sound good to me.

Then I got him to start the engine....Output from the alternator 15.1v at around 1200rpm...to me this voltage is to high.

But I am only used to old cars...pre 2000.

Next question....if the alt is faulty and I think it is.....is it possible to replace the alts regulator....is this the sort of thing an auto electrician.or is it always a new alternator...I presume the regulator is internal in the alternator body.

Nick.

[chippie]

What make of alternator is fitted?

Delco Remy alts have a replaceable reg as do Bosch...

[nickjaxe]

Sorry dont know what make of alt.....it will be the one it came out of the factory with if that helps.

I take it 15.1v is way to high.

Is the reg replaceable with the alt on the car.

[chippie]

On the basis that the battery is fully charged I'd say 15V is too high for the output of the alternator.....


As for swapping the reg, Cant say I know tbh, either way I'd be inclined to remove it from the car, lessens the risk of doing any damage...

But you need to find out the make in order to determine if the reg is swappable or not....OR just take it off and go to ECP and get a new one...?

[nickjaxe]

Ok thanks.

[Rhubarb]

Leave it running for a few minutes and check it with fan,headlights,hrw etc..As I'm wondering if this has smart charge? In which case the voltage will be high after an initial start.

[valhalla]

Before condemning the alternator on this car, it might be worth checking all the fuse-links and screw-connectors on the top of the battery.

This car should have the classic GM multiway fuselink set-up on the top of the battery at the +ve post; effectively a series of links divests the power out to the various electrical circuits. The alternator on this car will be sensing its output locally, but if there is excessive corrosion under any of the fuselinks or connector blades, you might be seeing an increase in voltage proportionate to the volatge drop across any of these connections.

DISCONNECT BATTERY, then investigate all the blades and fuselinks for white corrosion under any of the screw/nut fixings around that area. The alternator and starter motor share (I believe) a common power-line which is fed from a link-after-a-link sort of series of blades; there are around three nuts that could all have loosened or corroded underneath, and the job is as simple as removal, cleaning, greasing with petroleum-jelly, and reassembly.

But....for everyone's sake and sanity, don't try and do this with the battery live....unless you really know what you are doing......