Alternator not charging at low rpm.

tomstickland

I think the alternator is much more likely to be the problem. Battery is about 15 months old. Belt is fine. The lack of voltage when engine is running and the way that things picked up after I revved it for 2 miles suggests alternator to me.

ohreally

Tom, does the charge warning light glow slightly when you turn off the ign switch? If it doesn't that may indicate an alternator charging problem - this is a rough and ready roadside indicator and is not a definitive diagnosis....just an old trick from days long gone.

tomstickland

There have been some incidents of various warning lights glowing when I start the car up.

Pew_Pew_Pew_Lasers!

Could be a faulty regulator.

goldspanners

a few years a go i had an amplifier in another car of mine,the main positive feed to the amp in the boot from the battery had heat up and the insulation had melted and it occasionally arced off the body underneath, i only found this out 2 alternators later and when i was removing the amp and wiring i found the open part of the wire,the guy i sold it to put another alternator in it after i removed the wire and it charged perfectly all the time.
any time ive had the regulator go on an alternator it has usually over charged the battery,but im sure it is worth your while removing it and freeing the brushes off,if the regulator can be replaced go to a lucas or prolek and get a replacement regulator,this will only cost £10 or less,compared to a full alternator. 9 times out of 10 if the alternator is faulty it is the regulator that is causing it.

tomstickland

Well that was an adventure!
I made it about half way to the scrap yard when the electrics died.
I connected up the spare battery with jump leads, there was a bit of a spark, but I couldn't get the engine to turn over.
So I phoned up the breakdown service.


With nothing to lose, I removed the alternator from the car. I then undid the two screws that hold the brushes in place. Looking inside I noticed that one brush was shiney, whilst the other one had a darkened look to it. I guessed that this mean that there was poor contact, so I wiggled the brush aroud to encourage it out of its hole a bit more.

I put it all back together and tried starting the car. It was a bit slow turning, but it fired up and then sat there in steady idle.

I quickly put all the other bits back on, dumped the tools in the boot and drove to the breakers yard. It ran absolutely fine all the way there.

They had a completely reconditioned alternator for £85, so I bought that and swapped them over in the car park.

ohreally

You can now repair your own at your leisure and keep it as a spare or sell it.