Dead battery or alternator?

[foobar]

Evening,

I just got back from filling up for the week, when I noticed the voltmeter looked a bit low. I pulled over just to check and switched the engine off, tried to start and it wouldn't I managed to get it started while I was on the phone to the RAC and planned on taking it for a run - I do 60 miles a day though so a battery shouldn't be flat.

On my way home the voltmeter dropped to zero, the discharge, SRS and ABS warning lights came on, the LED clock and touchscreen display went off (although the touchscreen was flickering on breifly), and eventually the gearbox mode light went off.

Does anyone know where I need to start looking? It won't start at the moment. It doesn't sit around so there's no reason for a flat battery, I can only think one (or both) have died, or it's the alternator.

Thanks,
Steve.

 

[Dave2000]

Start with the terminal plug at the back of the alternator.

regards

Dave

 

[Roger]

^ good call on checking all connections from the alternator.

Modern batteries do tend to die very quickly these days - often without the old school signs of slow starting and hanging on for a bit - often they just fail. We have just had our first step into colder days and that can highlight a weak battery very quickly.

You can test the alternator at home quite easily with a simple voltmeter set to read 0 -20v = you should be getting a reading of #13.5 volts with the engine running. If you measure the battery not running and its below #10.5 volts then its probably dead - some fancy chargers can bring them back from the brink but as you said your is regularly charged I doubt they would in your case.

Your local spare parts / autofactor should be able to "drop test" it for you - if not completely flat / dead.

How old is the battery? Whilst you hear about batteries 10 to 15 years old, anything over 5 years would point me to that before the alternator.

Did you notice the red "no charge" light on before the flat battery?

 

[Dave2000]

As above but would add the batteries must be disconnected from each before testing with a drop tester, IIRC on the 100 there are two permanently in parallel? Do not run engine with batteries disconnected.

regards

Dave

 

[foobar]

Thanks all. I'll check the alternator connections when it's light and not raining. No idea on battery age, I've had the car about six months.

The only thing I've noticed over the past two times I'd started it, is that it didn't fire up instantly as it always does, took about half a second longer. It was only today I noticed the dash voltmeter was reading low, but I've had no warning lights at all until driving home today.

I've check both batteries with a voltmeter, engine off, and both read 11.75V +/- .02V, but I haven't checked either under load (I'll see if I can start it later, last I tried it wouldn't). I think I need to check the alternator.

Thanks,
Steve.

 

[StarCruiser]

As above Steve, it sounds like primarily the alternator is not charging. You should in fact get 14.4v from a fully functioning alternator. 13.8v is the minimum voltage required to begin charging the battery. If the voltage at the battery terminals is below this with the engine running at fast idle then there is a problem with the alternator or the connections to/from it.

 

[uHu]

and get those batteries charged right away. Otherwise they will be dead pretty soon. Normal starter batteries do not like to be fully discharged, They quickly loose their capacity to ever be able to be recharged again.

The fact that you have close to 12 volts on a fully discharged battery shows that you don't have a shorted cell at least.
Guessing bad alternator, based on the description of how it died -- that the voltage went down with the engine running.

 

[foobar]

Yes it's looking like the alternator isn't it, particularly since it all happened while I was driving. I guess it had had some issues over the past couple of days and wasn't charging much, if at all, then finally died this afternoon.

I owe so many people beverages-of-their-choice for all their help since I joined, thanks

Steve.

 

[Dave2000]

Given you added the recent problem with starting, it might be worth checking the fusible links on the R/H battery. They are at the age where they are beginning to rot. Try the cheap stuff first.

regards

Dave

 

[clivehorridge]

Yep, from reading the forum over the years, its check connections, check connections and check connections again, first.

The one on the back of the alternator is notorious, so start there.

If it's any help at all, the nice voltmeter that Chas gave me as a pressie tells me 14.4 V when running (charging) and 13+V at switch off. It reads something like 12.8V or 12.9V first thing in the morning, and then kicks up to 14.4 V after start-up when running.

Day in day out, the same story.

 

[nick_the_fish]

Check your alternator belt. It might be that its stretched a bit or come a bit loose.

 

[StarCruiser]

Check your alternator belt. It might be that its stretched a bit or come a bit loose.

Valid point there Nick. This is often accompanied by a squealing when the engine is revved…unless the thing's fallen off altogether that is.

 

[foobar]

The belt is ok, the connector is connected although I can't reach it to ensure there's a good connection. It doesn't look burnt out or anything, of course that doesn't mean it isn't faulty.

I think I'm going to have to get it to a garage. Apart from having no ABS or airbags and running down the batteries while I drive it, will it be OK in that state to drive?

Thanks.

 

[foobar]

Right, booked into my preferred garage. What are my chances of making 30 miles with no alternator?

Hopefully the RAC will be able to tow me there from half way.

 

[Roger]

I have no experience in the 100 - but I have done 150 miles in the 80 series 4.2 diesel when the alternator failed and it still started fine after. Certainly on the 80 power draw isnt great, a few relays and the like but nothing significant.

 

[Garfieldus]

Why not take it out and bring it to the alternator man and get him to check it?

 

[foobar]

I'd like the time to be able to do that but I've got to get back into the office, I've been working from home this week and I have an impending vet visit (for the cat, not for me) on Monday.

I'm still charging the other battery so if it finishes before it gets dark I'll risk it with everything turned off, wish me luck

 

[foobar]

That was uneventful at least. Put the batteries in, drove 30 miles, no lights on the dash whatsoever the whole time.

I checked both batteries as soon as I got there with the engine running, both at 12.47V, should be higher than that with the engine on. He'll see if he can refurb it before replacing.

Cheers all.

 

[chris58]

Hi Steve, did you find out what the problem was? The exact same thing happened to me last night!

Chris

 

[foobar]

It was the alternator, I had it replaced and the new one then turned out to be faulty because it would stop charging randomly. Had that one replaced under warranty only a couple of weeks ago, so far so good!

Steve.