Battery/Generator warning

[lhdctrevorandhazel@btinternet.com]

My 2010 997 Carrera has a battery/generator warning showing. However the battery is fully charged and even with all lights and heater fan on etc the battery is still keeping its charge when running. Does anyone know why the warning is on as the car is functioning normally and no fault code is shown on diagnostics. Can the warning light be reset?

 

[tscaptain]

Moved to 997 forum.
Do you know what the voltage is with the engine running? A Google search shows some instances of a warning light when all is otherwise well - the diagnoses all seem rather inconclusive. Poor connection somewhere?

 

[lhdctrevorandhazel@btinternet.com]

Yes, the voltage when the engine is running is 13.6

 

[STiG911]

Bit difficult to diagnose without additional details:
Was the car standing for more than 10 days or so before being started / driven
Did this happen after a period where the car was started and turned off, e.g. driving to two or more locations in succession?
How old is the battery - I'd expect a 2010 car to be on it's second by now at least. If it's not, I'd look to that first.
Usually a 997 battery will last four to five years.

Bear in mind that a battery can give a good charge reading while the engine's running (suggesting the alternators OK) but still not have enough amps, which would result in weak cranking when trying to start.

 

[lhdctrevorandhazel@btinternet.com]

The car had been standing for long periods over the winter, although on trickle charge most of the time. The battery is about 2 years old and is a Yuasa with it's own indicator lights for good, recharge or replace. It constantly shows green for good. My Son came home from abroad in March and has been sharing both of our cars, so, the Porsche has been in regular use for both short and long runs since then. The warning light came on on a return trip back to Norfolk from Dorset last week and now comes on every time you drive off from standing.
The voltage when off is 11.8 and 13.6 when running. The cranking on starting is strong. In fact there are no symptoms of an undercharged or weak battery apart from the warning light.

 

[m300raj]

Did you get this resooved as my car is doing the same it has had a new battery and alternator showing 12.4 when off and 14.5 when running no fault codes
thanks

 

[TheYorkshireFlipper]

Did you get this resooved as my car is doing the same it has had a new battery and alternator showing 12.4 when off and 14.5 when running no fault codes
thanks

I’m hoping that if not the OP, then perhaps you may be able to give an update as to the cause of your warning light issues please?

I’ve recently changed the battery and alternator on my 2005 C2s, (Yuasa battery and a Design911 own brand alternator), and I too am having the same warning lights on the dash.

No issues with a slow crank, and back in May when I removed the engine to replace all of the coolant pipes and hoses, I had my main engine wiring loom repaired and tested by a reputable wiring loom repair shop.

The bad news is that my MOT is due this week, and the Wife and I have a week away in France booked for the end of this month, so I could do with getting this issue sorted, otherwise we’ll have a long walk / swim to France.

Thanks in advance.

 

[Motorhead]

With a battery, alternator and wiring loom replacement or repair it sounds as though you’ve covered the potential principal causes of your problem. I would have thought that any earthing issues would have been negated with the wiring loom attention, but it would be worth double checking. I assume that the battery voltages are in spec with and without the engine running?

Can you run a diagnostic check to see if any errors are thrown-up to give you some guidance?

Jeff

 

[TheYorkshireFlipper]

With a battery, alternator and wiring loom replacement or repair it sounds as though you’ve covered the potential principal causes of your problem. I would have thought that any earthing issues would have been negated with the wiring loom attention, but it would be worth double checking. I assume that the battery voltages are in spec with and without the engine running?

Can you run a diagnostic check to see if any errors are thrown-up to give you some guidance?

Jeff

Thanks for the reply Jeff.

I’ve presently got three persistent warning messages / lights on my dash.

Rear brake pads low (they’re not even half worn)
SRS / airbag error message and constant warning light
And an intermittent battery generator (alternator) warning light.

I’ve just cleared all fault codes, but each one of them comes back on straight away.

The battery generator warning comes up as soon as the car is started, then goes away for as much as 30 minutes before reappearing again.
It seems to do so whenever extra load is put through the electrical system, (windows etc).

I aiming to fix the SRS issue first, as that is a definite MOT failure, (showing codes 803A and C141).

The only diagnostic I’ve done with the alternator this evening is to measure battery voltage as soon as the car is unlocked, (12.44v), which is a little low.

On the assumption that I can sort the SRS issue this evening, I’ll hook up the trickle charger and see if returning the battery to full voltage (13.5v) helps matters.

I can see this evening being a loooooong evening. I hate doing electrical diagnostic work.

One further thing to note is that upon reinstalling my engine / gearbox, whilst it fired up first time, I did have all sorts of weird and wacky electrical issues and a dashboard lit up like a Christmas Tree.
Literally nothing worked until I’d driven the car for nearly an hour, whereupon one by one, various electrical systems started to wake back up.

I didn’t have the battery generator warning at this point though. That only reared its head a few weeks later when my alternator was genuinely kaput.

 

[malarcy]

My suspicion is that the replacement alternator simply isn’t up to spec. The charge light is triggered by the dme - if it sees voltage below threshold on the exciter wire when it see the engine is running then the light comes on.

The voltage only needs to drop to a certain level and then the light latches on until next ignition cycle. By the time you have started the car and the measures the voltage (which by now is at a proper level ) the dme has already said “bad”

I saw this recently with a 3rd party alternator and it was only spotted with an oscilloscope trace of the exciter voltage (from alternator to dme) as the car was started.

 

[TheYorkshireFlipper]

My suspicion is that the replacement alternator simply isn’t up to spec. The charge light is triggered by the dme - if it sees voltage below threshold on the exciter wire when it see the engine is running then the light comes on.

The voltage only needs to drop to a certain level and then the light latches on until next ignition cycle. By the time you have started the car and the measures the voltage (which by now is at a proper level ) the dme has already said “bad”

I saw this recently with a 3rd party alternator and it was only spotted with an oscilloscope trace of the exciter voltage (from alternator to dme) as the car was started.

Thanks for that Malarcy. Very insightful, and a good call on using an oscilloscope, (although I don’t have one).

My Wife and I (she’s an engineer by trade, oil / gas / nuclear), came to the conclusion about the SRS warning lights.

I did the Race Against The Sun back in June, and only just managed to get the car ready in time. The fitment of the rollcage was bodged a little. We think we’ve damaged the seatbelt pre-tensioner system on the passenger side.

Roll cage was removed last night, (and will be put up for sale soon), but the SRS issues still persist.

Alternator?

Pre-start voltage yesterday was 12.44v
The vehicle was trickle charged all last night and today, until the 7th (green) light illuminated on my CTEK.

After which, battery voltage was 13.36v
And with the engine running, 13.10v

Whilst those figures aren’t super low, they are a little bit low IMO?

The battery had gone completely flat a couple of times prior to fitting the new alternator, so I’m now wondering if this is related to a slightly low voltage issue, hence why when fault codes are cleared, the warning lights still reappears.

I’m loathe to go firing the parts cannon at the car though in the hope that something works. That can get expensive quickly.

 

[malarcy]

I have heard several very similar stories lately. Don’t know what’s special about the charging but this is probably the 4th one that I have heard of recently.

That said. One of them was fixed by a d911 “oe match” alternator , another car problems started when one was fitted.

There are several variants for model year and tip vs manual I just wonder if somewhere there’s a supplier of regulator components whose pushing a bad batch.