Ignition light comes on when driving?

[colinwoods]

Hi all.

Today, when driving, the ignition light came on and the Volts gauge started depleting. The light would then go off and the Volts gauge would rise again, clearly charging the battery, it then did this again throughout my journey home (70 mile trip).

By the time I got home the ignition light was constantly on the Volts meter depleted to 11 and stayed there...

Some relevant back ground... Since replacing my alternator around 6 months ago, along with a new battery, the Volts gauge has lived in the 15+ (maximum) and would sometime drop to 13.5. I've had a headlamp go but nothing else, apart from my windscreen wipers acting like they have been on steroids! So I assumed this would be OK?

It seems to me that maybe the alternator has gone faulty and needs replacing, but it's only 6 months old?

Any thoughts or experience?

[xvivalve]

First things first; how tight is the alternator belt?

[Mad Mart]

You should be seeing around 14.5V with the engine running. If you have a multimeter (even a cheapo one), check across the battery terminals whilst it's running. If you are seeing 15V+ it is probably the voltage regulator in the alternator. Quite an easy and cheap fix.

[Carledo]

The Voltmeter fitted to our cars is not particularly accurate, but I would have been concerned to see a reading consistently over 14.5v. And your high speed wipers is indicative that the voltmeter was telling the truth and the alternator was indeed overcharging.

Overcharging is worse than not charging at all (voice of experience here) and can lead to the battery literally melting and choking the car's occupants with acid fumes, been there, done that and have the T shirt, My Gt6 convertible did it on an evening run down to London, at Oxford services (when the M40 stopped at Oxford) I pulled over because the fumes from the boot mounted battery were killing me, to discover that the battery sides had melted from the heat inside and spilled acid was eating the fuel can next to the battery. Having nothing else to do, I disconnected the alternator plug and continued to London, having to bump start the car as the battery was fried. I just about made it! The battery did recover eventually with water added and a slow charge, but it was never quite the same - and of course I had to replace the alternator. I also fitted a voltmeter at that juncture, so I wouldn't get caught out again!

As far as I can see, your alternator may have been duff from the outset and has just taken time to knacker the system.

Steve

[colinwoods]

Thanks guys.

So, the fan belt is tight. Funnily enough, it was constantly making a screeching noise when I over revved it, but as soon as the ignition light and battery issue started today its sopped screeching?
I was planning on replacing the fanbelt as they are cheap, as I figured this was the noise. To be honest though, the belt looks fine (deep teeth etc) however I thought I'd change it anyways.

Would the screeching be related to the fanbelt?

[Mad Mart]

I think the screeching is linked to the over voltage being generated by the alternator. The alternator needs more work to turn it hence the fan belt slipping.

[colinwoods]

I concur, what's the solution though? New alternator?

[Mad Mart]

No, just get a new voltage regulator for the alternator.

http://www.ebay.co.uk/itm/CARGO-130637- ... Sw8-tWZAlu

Two screws to remove the plastic cover. One screw for each connection and one screw holding the VR in place.

[colinwoods]

Excellent! I've ordered one and will keep you posted.

Thanks!

[colinwoods]

Hi all,

So I replaced the voltage regulator in the alternator but the ignition light is still on and the battery/volt gauge reads 11.5v.

I will get my hands on a. Voltage meter reading thing for the battery and will report back, however what's your thoughts at this stage?

[Jon Tilson]

I suspect your brushes are also shagged...

Just get an exchange alternator. You can learn to repair one further down the tracks and there are loads of youtube videos of variable quality that tell you how to do it all.

For now you want to get it running and learn to do the more fun stuff, like ignition and carb tuning.

Jonners

[Mahesh]

I have my old alternator if you want to try before you buy.
Only it's at my other home and I won't have it with me till Monday.

Was working fine 22 years ago and was only used for 8 months.

Correction, was working fine when I collected the car from Dorset last October.

[colinwoods]

Thanks Jonners, thanks Mahesh!

Mahesh, I'll take you up on that offer. PM me your details and we'll arrange.
I'm at brands hatch tomorrow for blancpain GT thingy so it's better for me to pick it up after anyways.

NB: is it ok to drive my car with ignition light on and a ticky alternator? Car is sounding and running like a beauty?!

[Jon Tilson]

Fully charged battery will last about 15 hours on ignition only....

Jonners

[Mahesh]

Found the alternator yesterday evening.

PM sent.