Warning light - cold morning

[rgc610]

Hi all,

Hoping you can help - this has been an ongoing issue for over a year now!!

Occasionally on winter mornings, my comfort access would stop working and the head lights wouldn't come on when I unlock using the fob. I would then start the engine and I would have the warning light of an AMBER car on ramp, alongside clock resets etc.

I took it into my garage as I had service anyway and they said this was the light for brake pads so they replaced the brake pad sensor (as brake pads were fine). This appeared to fix the issue for all of 3/4 days (I believe the weather was marginally better over these 3/4 days and it was a coincidence).

Came into spring summer and issue never occurred so I did not worry until this winter when it started happening again. As the comfort access wasn’t working, headlights weren’t turning on when unlocking car through fob, folding top was no longer going up and down through fob etc. I decided it was the battery - forums seemed to support this. I booked it in for a battery health check and they said it was significantly depleted. This made sense as it still had the original BMW battery (from 09).

I replaced the battery and for the first couple days - everything was perfect! Folding top, lights, comfort access. No warning light - worked perfectly.

After about a week I realised the lights stopped coming on again and now the folding top isn’t working through key fob. However, comfort access is always working. ONCE in the morning the warning light came back on but this was only once.

I’m convinced it is the battery but as I’ve replaced it I am now stuck on how to proceed? I really want to get this fixed now so any help would be much appreciated!

 

[Anonymous]

Well it sounds like your alternator is not charging your battery adequately..

How old is the car? Which model?

How many miles do you drive when the car goes for a run/ what type of driving , open road , town..?

 

[rgc610]

Thanks for your reply.

I didn’t think it was the alternator personally as when I am driving everything is fine?

E89 09 plate. 75k miles. Drive 6k miles a year. Daily run.

It may also be worth saying that after turning engine off and listening to radio for approx 1 minute, the yellow battery symbol comes on and radio turns off. Not sure if this is normal or not to prevent battery from draining?

 

[Chippie]

Certainly sounds like the battery to me
When you had the new battery fitted was it coded to the car, it may still think it’s still got the old battery, or as suggested the alternator isn’t putting out enough to fully charge the battery after running the engine, lights, etc.

 

[rgc610]

Hi,

Yes it was coded. Paid Halfords to do this.

Is there a way for me to test the alternator?

 

[scootr]

Hi,

Yes it was coded. Paid Halfords to do this.

Is there a way for me to test the alternator?

One simple way is to connect a voltmeter to the jump posts under the (ah) bonnet and note the battery voltage.
Then start the car and note the voltage - it should be up considerably. Best if you can position the meter so you can read it through the (ah) windscreen. That way you get lots of battery information... like starter draw down and the alternator's initial bulk charge and sustained charge.

 

[Anonymous]

Well if it’s a new battery, correctly coded, of the right type it can only be the alternator...or it’s control circuit....

So either it’s a faulty alternator ,judging by plenty of people offering re-furbs it’s a relatively common event on bmw

Or faulty accessory belt drive

Or it’s a fault in the DME to Alternator control

Or the battery state unit next to the battery...iBS

Unfortunately with the regenerative charging circuit the simple reading of battery voltage engine running / not running is not a direct measure of a correctly working system...

Clearly your battery is flat as, for example I can run my radio with power amps for at least 30 minutes with the engine off..

It’s a job I suspect for an auto electrician to trouble shoot..

However given where you are at a voltmeter should show around 12.2 v on the battery all switched off..minimum..normally 13v ish

Once engine running voltage should rise initially to 14v ish given flat battery

Best I can offer..

 

[rgc610]

Hi,

Yes it was coded. Paid Halfords to do this.

Is there a way for me to test the alternator?

One simple way is to connect a voltmeter to the jump posts under the (ah) bonnet and note the battery voltage.
Then start the car and note the voltage - it should be up considerably. Best if you can position the meter so you can read it through the (ah) windscreen. That way you get lots of battery information... like starter draw down and the alternator's initial bulk charge and sustained charge.

Hi, thanks.

My old battery was at about 12.2V when engine off which led me to replacing. I’ll check what the new one is tomorrow. If this is also low then as it’s a new battery, this would suggest it’s the alternator not charging sufficiently?

Could I damage the battery by not sorting alternator immediately? I have my service due in April.

 

[rgc610]

However given where you are at a voltmeter should show around 12.2 v on the battery all switched off..minimum..normally 13v ish

Once engine running voltage should rise initially to 14v ish given flat battery

Best I can offer..

Thanks. So 12.2V when off would show flat battery. If this rises sufficiently to 14V when engine on, what would that show?

 

[scootr]

Pbondar, I think your numbers are conservative. Curious to see what he gets. And would like to know what the low voltage marker is when the starter is turning the engine before it starts. A weak battery would tell the tale there.

 

[Anonymous]

However given where you are at a voltmeter should show around 12.2 v on the battery all switched off..minimum..normally 13v ish

Once engine running voltage should rise initially to 14v ish given flat battery

Best I can offer..

Thanks. So 12.2V when off would show flat battery. If this rises sufficiently to 14V when engine on, what would that show?

Shows the alternator is charging ...like I said the charging system is very complex, well beyond home diagnostics for most people..

The other thought overnight is whether your car has a circuit running constantly draining the battery..aftermarket goodies and some early Bluetooth oem fits had issues in this area...

Needs an auto electrician I recommend

 

[Christrong]

I’m going to feel really stupid after writing this but I assumed that because it was using regenerative braking there was no alternator. I guess I don’t understand what regenerative braking is then.

 

[Anonymous]

I’m going to feel really stupid after writing this but I assumed that because it was using regenerative braking there was no alternator. I guess I don’t understand what regenerative braking is then.

It’s ok not to know everything..

Many articles here is a simple explanation


https://www.ppsl-bmw.sg/insights/Brake-Energy-Regeneration

So still a battery and an alternator but complex logic and management....joe Lucas prince of darkness type electrics a distant concept..

 

[ph001]

I’m going to feel really stupid after writing this but I assumed that because it was using regenerative braking there was no alternator. I guess I don’t understand what regenerative braking is then.

You are not alone. A few people think that regen braking uses some kind of dynamo on the wheels to transform the kinetic energy of the car into electricity when braking! It's actually nothing quite so scientific - simply that the alternator is only used to charge the battery when braking / coasting. The premise being you don't actually need the alternator connected all the time loading the engine. The broad term BMW use for it is 'Efficient Dynamics'

There are all sorts of algorithms to determine if / when the alternator is engaged based on battery voltage / capacity etc. That's what the IBS module on the battery is used for.

 

[R.E92]

If the battery still reads 11.6V or higher in the morning before starting then it's fine. Most will be around 12V or higher if fully charged but I've started up with it down at 11V without any errors of difficulty cranking.

You can check the voltage at the terminals when the car is running and it should be above 14V to show that the alternator is healthy.

Another cause of issues like this are corroded grounding straps. The main one is on the passenger side engine mount, not sure if it's visible from above or not. If I were you I'd double check all grounding straps before spending more money on troubleshooting since it costs nothing and is relatively easy.

 

[rgc610]

Thanks for all the posts. Took some measurements this morning.

Engine off = 11.89V
Engine turning on = approx 10.5V
Engine on =14.7V
Engine off again = 11.9V

No warning light since but car roof still won’t go down using key fob and lights don’t come on when unlocking car with fob.

What do the above measurements show?

 

[flybobbie]

Go buy an AGM compatible charger and charge the battery. That way you can eliminate any battery problems.
If then everything works ok, you will then know it's a charging problem.
Always good anyway to own a charger.
Even with good voltages, batteries can do weird things. I've known them show 12volt, but still not crank a engine.

 

[rgc610]

Go buy an AGM compatible charger and charge the battery. That way you can eliminate any battery problems.
If then everything works ok, you will then know it's a charging problem.
Always good anyway to own a charger.
Even with good voltages, batteries can do weird things. I've known them show 12volt, but still not crank a engine.

Thanks for your response. If I just connected it to another battery for a while would that do the job? Would like to avoid spending more money if I can - new battery was £200

 

[flybobbie]

Go buy an AGM compatible charger and charge the battery. That way you can eliminate any battery problems.
If then everything works ok, you will then know it's a charging problem.
Always good anyway to own a charger.
Even with good voltages, batteries can do weird things. I've known them show 12volt, but still not crank a engine.

Thanks for your response. If I just connected it to another battery for a while would that do the job? Would like to avoid spending more money if I can - new battery was £200

Erm no, i wouldn't do that.
Do the job properly use a charger, as it will condition the battery properly by varying the charge.
Keep in mind you do not know how long a new battery might have been on the shelf.

 

[ph001]

Go buy an AGM compatible charger and charge the battery. That way you can eliminate any battery problems.
If then everything works ok, you will then know it's a charging problem.
Always good anyway to own a charger.
Even with good voltages, batteries can do weird things. I've known them show 12volt, but still not crank a engine.

Thanks for your response. If I just connected it to another battery for a while would that do the job? Would like to avoid spending more money if I can - new battery was £200

No, you need a voltage above 13.6V to start the charging process. Your battery volts in the morning seem a little low. If it’s below 12v it almost completely flat. Fully charged is about 12.6v in the morning.