Red Battery Light

[Medium Dave]

This morning the red battery warning light appeared on the dash and stayed there. When I got home (only a very short trip just to dry the brakes after I washed the car) I shut the car off and left it for half an hour. When I tried it again, the light had gone. The reason for this post is that this has happened before. On that occasion (well, two occasions close together) the fault code logged was that the alternator was not recognised as being the correct one. That confused me because I think it is the original alternator (the Z is a 3.0 2003). The alternator has caused no further problems until today so it seems to recognise it most of the time.

Has anyone else experienced this? I thought maybe it was water in the electrics somewhere after I washed the car but last time was in September and I am positive it had not just been washed (nor was it raining).

Any ideas?

 

[AlanJ]

Not sure how the vehicle can 'recognise' a non OEM alternator as it is the output from the alternator which charges the battery. The best thing to do is to check the alternator output - you will need a test meter to do this or get your local friendly garage to assist. Park with handbrake on in P if auto. Go to the boot and access the battry compartment -start the Zed and read the voltage on the battery terminals using the meter - this voltage should be between 13.4v and 14.5v approximately and steady. Get someone to switch on various accessories and see what happens to the voltage - this may briefly dip as items are loaded onto the electrical system but quickly resume to its original reading (between 13.4v and 14.5v). If the voltage drop is maintained as items are loaded (lights, heater fan, ac etc) then the alternator is on its way out. It could also be that an over zealous wash has made the alternator drive belts slip and as 'engine heat' has dried the engine bay normal tension has resumed allowing the alternator to work properly. No doubt others with have other suggestions.

 

[cj10jeeper]

I wouldn't worry about it unduly. Mine does it from time to time (perhaps 3 times in 6 months) and usually if I get the car out of the garage, switch the engine off and then start it again. The battery light comes on.
It will stay on for the whole of that journey and resets only once the engine is stopped.

Run all the tests that Alan says as they are good, but I'll put money on it nowt of interest comes of it if your car is starting easily, not struggling to turn over, etc. I know my charging circuit is in tip top condition and a brand new battery in place.

 

[Medium Dave]

Thank you both for your replies.

I have already had the alternator checked out by my local indy - apparently no problems. I will do the tests as AlanJ suggested but it makes me feel more confident that it happens on cj10jeeper's 2003 as well.

cj10jeeper - if I were on a long journey, should I be worried that the red light is on or can I just continue?

 

[cj10jeeper]

In my experience just continue if you are finding that it resets once you stop and restart. If it remains on after some considerable mileage and comes on again when you restart get the battery checked. It's stayed on once on mine on 20 mile plus trip.

Worth giving the battery a good charge on one of the trickle and maintenance chargers, however if it keeps happening on a regular basis something is amiss

 

[Medium Dave]

OK, thank you.

It does reset but not straight away. If I switch off and restart immediately then the fault remains. If I leave it a bit longer then it seems to clear.

 

[cj10jeeper]

OK, thank you.

It does reset but not straight away. If I switch off and restart immediately then the fault remains. If I leave it a bit longer then it seems to clear.

Yes - that would be consistent with the car having to fully shutdown after 15 minutes or so

 

[Medium Dave]

You have put my mind at rest. Thank you.

 

[majeric]

This has stared happening to me since I had my quad exhaust fitted.

Fitted a new battery but still happens.

Any ideas?

 

[bcworkz]

Check the main battery line going forward from battery for damage. It is a monitored line and unexpected electronic characteristics will cause an error condition, even though it actually works fine.

Not sure how the vehicle can 'recognise' a non OEM alternator

Quote from years ago, but for the record, the alternator has a digital serial interface with the ECU. If an aftermarket alternator was not properly reverse engineered, it could confuse the ECU, causing it to throw an error condition.

 

[majeric]

Took it to a garage today.
Checked the voltage at the battery with every switch on in the car - was just above 12 volts.

Then turned everything off and again, was just above 12 volts.

Conclusion is that the alternator is screwed.....does that sound right?

 

[bcworkz]

Engine running, yes? Then yes, you should get well over 13 volts. But could just be the regulator, don't know how to test though. Somebody else will know.