MK2Potential Alternator issue - how long should the light stay on ??

[kt66]

Really pleased with this Mk2 1.0 Ion I've bought for my daughter 2007, one owner full Toyota history and it's great.

One quesiton is that the battery/alternator light stays on for maybe 30 seconds during the day and then maybe 3/4 minutes at night when the light is on.

Is this normal? is the alternator on the way out? or could it be that having stood for a few weeks it's getting itself back into shape.

Appreciate any thoughts.

Thanks

[bathtub tom]

I'd check the belt tension. Does it squeal when started from cold?

[kt66]

Thanks for that- yes I'd checked the belt and it seems ok and no squealing. What I can't get my head around us that the light goes off eventually which suggests that the alternator may be working, but not very well??

[bathtub tom]

My experience of alternators is they either work consistently or fail, not that they take a while to 'warm up'. Don't take that as gospel, I'm sure there's many faults I've never experienced.

Are they still 3-phase devices? I once had one phase of a diode pack go down. Could you have a similar problem, meaning the alternator's only working at part efficiency, thus charging at a much reduced rate?

Try an auto electrician who may be able to help. I found my fault by looking at the output on an oscilloscope - don't know if anyone still knows how to use one today!

[kt66]

That makes sense actually - working at a reduced rate. I'll see if I can find someone who can do it.. Does seem odd though as you say they either work or they don't.

 

Thanks

[alan333]

If you have a multi meter put it across the Battery and see what volts you have with/without the light/engine on.  It should be around 13 volts with the engine switched off, and around 14 volts with the engine on.  If it's showing a lower voltage with the engine on then it's not charging.

[kt66]

OK, will do, thanks. Just noticed you have a 1.8 - that must be really quite nippy....

[alan333]

1 hour ago, kt66 said:

Just noticed you have a 1.8 - that must be really quite nippy....

Sorry kt, my profile is a bit misleading.  Mine was a 1.8 Avensis (the most recent of a few Avensis I've owned, and we also had an Auris), but I changed my car to a Mazda 6 about a year ago, and then changed again to a Mazda CX-5 just recently.  I felt it was better to keep my profile with a Toyota car, so I left it as it was.  I enjoy the TOC forum so I still keep fairly up to date on it (even tho I'm a deserter lol), hopefully along the way I help an occasional member out from time to time.  I totally agree tho - a 1.8 Yaris must go like the wind!

Good luck diagnosing your car, FWIW my money's on the alternator :)

[Mooly]

It could also actually be the Battery at fault.

Traditionally the alternator light was fed from a separate low current diode pack within the alternator with the main charge feed to the Battery fed from the main high current diode pack (and yes they are still 3 phase machines). If there was a difference in voltage between the two then the light would illuminate.

I suspect the modern instrument pack uses electronics to convert the old flickering warning light into a constant display.

A Battery that has stood overnight will probably show around 12.2 volts, perhaps a little higher if fully charged. After starting, the voltage across the battery should immediately rise to around 15 volts (or even higher in very cold weather... the alternator is temperature compensated to do this and the higher voltage will really hammer the charge into a battery following a cold start) but the voltage will fall back within a minute or so to around 14.5 volts. As the alternator gets hotter the voltage will fall more. A hot summers day with a hot engine will see the charge voltage at around 13.5 or lower.

A faulty battery could actually allow the voltage to rise to high possibly triggering the warning light. Any cheap multimeter will read DC voltage accurately enough to gauge if there is a problem.

The voltage should hold up at idle with headlights and heated window on.

Also make sure the battery terminals are secure.

    

[kt66]

That's a very good response, thanks.

I'm at home tomorrow so the multimeter is coming out to see what's what. Lucky that the weather is so good.....

I'll keep you posted- it's exciting stuff eh!!!!

[Mooly]

OK, good luck.

[kt66]

That's a very good response, thanks.

I'm at home tomorrow so the multimeter is coming out to see what's what. Lucky that the weather is so good.....

I'll keep you posted- it's exciting stuff eh!!!!

[kt66]

Ok, so when it's cold the Battery is 12.3v and that doesn't seem to change (done it a few times throughout the day).

When running its reading 14.35 again fairly consistently.

What's the consensus?? Should I just let her run it for a while (it's stood for a few weeks before I bought it) or is it Battery or alternator....

I guess the odd thing is that the Battery light does go out but it just takes a few seconds with no load and a few minutes where the lights etc are on...

Help! Thanks.

[alan333]

Seems to be charging, but is it also charging while the light is on?

[kt66]

Yes, it seems to be a consistent 14.3V  regardless of what's on.....

[Mooly]

14.3v will certainly charge the Battery but you shouldn't be seeing the light come on. The light is triggered when the alternator output and Battery voltage differ. The devil is in the detail with this...

The fact that it takes longer to go out when the lights are on suggests the alternator is at fault and not producing full output, but its not definitive proof. You could do a rough and ready check on the Battery health by simply turning the headlights on (with the engine OFF) for 10 minutes or so. That will draw around 10 amps and is a walk in the park for a healthy battery. During that time the voltage should hold up above 12 volts. If it starts falling quickly and goes below 12 then stop the test and start the car.

A new healthy and fully charged battery would run the lights for 5 to 6 hours and so just 10 minutes is an easy load but it would be sufficient to show if the battery was obviously suspect.  

 

 

[kt66]

Thanks for that and that's a good way of checking it actually, I'll give that a go in the morning.

 

It seems something isn't quite right, but only slightly... I'd much prefer it to be Battery if something is at fault though....

 

Thanks, will post in the morning.

[kt66]

Just done the test of leaving the lights on for 10-15 minutes and the Battery drops to about 11.5/11.6 which is interesting. Does that point towards Battery then?  I've left it on charge for now and will repeat the test later on...

Many thanks

[Mooly]

 I would expect it to hold up a lot better than that, and so that sounds highly suspect for a light loading such as lights. 10.8 volts is considered the absolute 100% discharged voltage for a 12 volt Battery and so to see yours heading that way so fast does point to a possible Battery issue.

Other valuable clues can be signs of individual cells gassing and audibly fizzing when under discharge. If the cells have easily removable caps then its easy to see gassing. If the initial voltage holds up for a few seconds under discharge and then suddenly drops then that is a sign of a failed cell that is way down on capacity.

Back to discharging the Battery again, and a healthy battery should easily support not just the headlights but also lights, heated window, wipers, electric windows going up and down a few times (don't overdo the windows as you will overheat the motors) for a considerable time.

You might find this interesting. Look at the second graph. Which ever way you look at it your 11.5 volts after just a few minutes is pointing toward a faulty battery. 

http://scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

 

  

 

[kt66]

Thanks for all these messages. Agree it did seem to point towards a Battery which is on the way out, but only a little bit.

Any recommendations on new batteries? There's a Varta on it at the moment though I've had recent good experience with Numax. I've also got a Halfords trade card which does bring it down a bit...

Thanks.

[Mooly]

Its a long time since I've had to buy a Battery so I can't really recommend specifics other than to say go for a well known brand with a good warranty (3yrs). Toyota reckon to be competitive on batteries so might be worth a call.

As to being sure it is the Battery. Well the tests so far seem to show it is highly suspect. My only concern is not knowing what the initial state of charge has been. Can we be sure it was 100% charged before beginning the tests ? If so then there is little doubt on the Battery being below par. 

 

 

[FROSTYBALLS]

A Toyota Battery will cost £95 - https://www.toyota.co.uk/caring-for-your-toyota/service-and-maintenance/repairs.json

[kt66]

Thanks for all of this. I think what I'll do is run it for a few days - it's had very little use over the last few weeks whilst it was being sold etc etc and see how things settle in. It does seem to all point towards the Battery though.

 

Thanks to everyone, really value the support on the forum - it's a really good example of how it should work. 

[Mooly]

You're very welcome and I wish I could be 100% certain and say yours is definitely the Battery but I still have nagging doubts tbh.

For curiosity I just measured the resting voltage on my Auris and our Corolla. Both have stood for 48 hours. The Auris does regular high mileage and reads 12.38 volts. The Corolla does minimal mileage (at the moment less than a couple of miles a week and probably under 300 miles in the last 12 months) and that reads 12.14 volts.

What I can say for sure is that with you having measured the standing voltage at around 12.3 volts, then any voltage over that figure is charging the Battery. Once you are over 14 volts then you are in the normal charging range. There is no doubt over that.

12.3 volts suggests a fair state of charge, particularly if it outside and the Battery is cold. The fact the voltage fell away when we did the lights test points to it being below par. Would that cause the light to come when initially started and charging ? That's where the doubt sets in.

In the past I've tried my Auris with headlights, front and rear fog lights, heated window and whizzing the four electric windows up and down half a dozen times or more over a 15 minute period to gauge how the battery was holding up. I can't remember the exact figures now but I remember there was no hint of the voltage falling off rapidly.

Seeing how it develops is perhaps not a bad idea. Keep us updated.

 

[kt66]

Thanks for that. I nearly bought a Battery today but then thought I'd give it a bit more time before I do. These Yuasa ones from Halfords sound good and have a five year warranty. (Incidentally when choosing it asks whether the car is a Japanese or a French build and then recommends different choices - I didn't realise they were made in France- how can you tell??).

I'll use it a bit in the next few days and see what's what (keep a spare Battery in the boot as well!).

 

Thanks