Battery Light keeps Coming On

[tmwsccsh]

Hi all,

Firstly, apologies that this is going to be a long post.

A few months ago I had problems with alternator and starter motor issues.  All was resolved when a new positive power cable from the battery to starter motor and replacement alternator was fitted at the end of July.

Well, about 6 weeks later and I am experiencing the dreaded battery light again. Symptoms are that occasionally after about 1 minute of being started, the battery light comes on. Power off, lock, unlock, start up again and all is fine until the next time it occurs. But it's annoying and makes me wonder if something more sinister is lurking there. I have noticed that if I turn the key to the position where all the dash goes live and leave it there for about 15 seconds then start the chances of the battery light coming on decrease greatly, but this is not guaranteed.

So far I have changed:-
- Alternator
- Starter Motor
- Positive Battery Cable

The battery was not swapped but has been tested three times as fine. 

However, tonight it was worse than usual...

5:35pm - got into car to come home from work. Started up and let it run for a minute, no battery light came on, headed home.

6:05pm - arrived home.

6:15pm - had to go out. Started car with no AC on, left it for a minute, battery light came on. Switched off, locked, waited 10 seconds, unlocked, started with no AC on, left it for a minute, battery light came on. Switched off, locked, waited 10 seconds, unlocked, started with no AC on, left it for a minute, battery light came on. Whilst the light was on I read the voltage from the battery - 14.31v. Seems normal to me. So, switched off, locked, waited 10 seconds, unlocked, started with no AC on, left it for a minute, battery light came on. Switched off, locked, waited 10 seconds, unlocked, started with no AC on, left it for a minute, battery didn't come on, so off I went. Turned AC on. About 10 seconds later, battery light came on. Pulled over at a safe point, switched off, locked, waited 10 seconds, unlocked, started with AC on, and carried on the journey. No more battery light - yay!

6:30pm - finally arrived local Sainsburys. Car turned off.

6:40pm - left Sainsburys. Started with no AC on, left it for a minute, battery light came on. Switched off, locked, waited 10 seconds, unlocked, started with no AC on, left it for a minute, battery light came on. Lost interest, started it up and drove off. About a minute into the journey, battery light came on. Switched off, locked, waited 10 seconds, unlocked, started with AC on, left it for a minute, battery light came on. Pulled over at a safe point, switched off, locked, waited 10 seconds, unlocked, started with AC on, and carried on the journey. About a minute later, battery light came on. Pulled over at a safe point, switched off, locked, waited 10 seconds, unlocked, started with AC on, and carried on the journey. About a minute later, battery light came on. At this point I didn't care as I was 20 seconds from home so just pulled onto the driveway and turned him off for the night.

I am fairly confident that tomorrow morning when it's time to go to work I will have no problems.

I have also noticed that once he gets going with the light not coming on, that's it - it stays of until the next shut off and maybe the problem comes back when I try to start again. Did 150 miles on Monday night after the light had come on 3 times trying to start after a quick stop off somewhere with no more repeats.

Someone has suggested there may be a sensor or similar on the alternator that could be causing the issue - can anyone identify where this is so I can check it out?

One more final bit of information that has hit me. When the original alternator failed over a year ago, the recovery guy suggested that the battery was also fried and would need replacing as well, however at the depot (had to change trailers) on the way back his boss had a look and said that he thought it would be Ok. This is the same battery that has now been on 2x failed alternators in the last 18 months or so. Is it possible that this simply is a battery problem? It has been checked but you never know, especially as it is getting worse.

It's just getting annoying now - I don't know if I trust the information that the batterylight is giving me based on all this. Also means I don't have a lot of trust in the car at the moment which isn't good - just wonder if it is going to let me down at some point...

Thanks in advance all and sorry for the long post.

Regards, 

Tim Watts

[JOE-DOT-COM]

hi

You need a multi meter and test what voltage you have there, no point guessing

You should have over 12volts at all times, more towards the 12.5 volts with engine off

with engine running it should be over 14 volts ideally 14volts to 14.5 volts, if it drops below 13.5volts running alternators it faulty, below 12.5 volts alternator fried

most alternators have brushes in them that connect to the armature, varying the voltage on the armature alters the alternator output, so as the brushes start to fail, alternator output current can fluctuate intermittent, until they fail all together, usual symptoms lights when on, lights brightness can flicker or fluctuate

you need to check the voltage on the battery and see what you get, if you get 14.5 volts and the battery light is on, then the fault could be elsewhere

also you can put the dash in diagnostic mode and monitor what voltage the battery is, but recommend using a multi meter first on the actual battery

cheers

Joe

[tmwsccsh]

Hi,

Sorry, should have said, the voltage reading I got was with a Multi-meter.

TMW

 

[tmwsccsh]

So, have done a few journeys today with the TEST mode activated so I can monitor the battery voltage.

Typically, no battery light today and I have now done 4x trips...

But, pattern seen thus far is, start up and there's around 14.2v (fluctuating slightly) and after about 3 minutes, this drops to around 12.4v (again fluctuating) where it stays for the remainder of the journey - from other postings I have read I believe this is normal but could be wrong?

Will see what happens on the return from work and other trips over the weekend...

TMW

[JOE-DOT-COM]

Hi

12.4 volts with engine running is too low,

check that your alternator is charging, as it sound like it is, because you said you had 14.3 volts at the battery

you need to check agaim when the fault is on and see what the voltage is on the dash and the battery with a multimeter, just to confirm the battery is charging, but for some reason the car electronic only thinks its see a lower voltage

which would lead me think, you either have a bad connection somewhere, or a bad earth give a low voltage on a control unit,

cheers

Joe

[tmwsccsh]

On 9/18/2017 at 8:13 PM, JOE-DOT-COM said:

Hi

12.4 volts with engine running is too low,

check that your alternator is charging, as it sound like it is, because you said you had 14.3 volts at the battery

you need to check agaim when the fault is on and see what the voltage is on the dash and the battery with a multimeter, just to confirm the battery is charging, but for some reason the car electronic only thinks its see a lower voltage

which would lead me think, you either have a bad connection somewhere, or a bad earth give a low voltage on a control unit,

cheers

Joe

He died yesterday :(

Recovery guy came out - battery effed.  Was only holding 2% charge from their testing gizmo.

Recovered to home, battery proof of purchase found, returned to place of purchase and swapped, but I paid the difference to upgrade to a higher-spec one.

All good last night, let's see what the weekend brings...

TMW

 

[StephStang]

Hi Joe!  My mom's Jaguar X-Type is exhibiting a similar problem.  Did you ever get yours resolved?  I'd like to resolve her issue before she ends up stranded.  

 

Thanks!

 

Steph