Car not starting. Battery or alternator or something else?

[Poloobs]

Hi guys,

My car has no electronics working when I insert the key in the ignition. Nothing turns on. So basically I can't even lock the car with remote. I have to use the key to lock the doors.

When I connect portable jumper starter to the battery, all the electronic works. When I start the car, it struggles a little but starts fine.

I left the car running for 20 mins (didn't drive) before turning the engine off. As soon as I turned off the engine all the electronics went out.

When I did the above things 2nd time and drove it little bit, the car shut itself down. When I jump start the car again the power steering stopped working. I managed to park but I haven't done anything after that.

Can you please tell me the issue with the car? Is this alternator or battery or something else?

Thanks.

[RUM4MO]

You really do need outside help to solve this, trying to give you help without you understanding much or having any tools like a DVM will not work too well I'm afraid, no insult intended.

It might just be a faulty battery and/or a faulty alternator and/or faulty wiring, so not something that you could rely on some help offered on a forum.

What I'm saying is, replacing that battery might solve all your problems - but if it didn't you would be a bit annoyed by going by what turned out to be duff help.

Running an engine for 20 minutes is not going to recharge a discharged battery, it needs charging a lot more than that to get it charged up again, that is if it is still fit to take on a full charge, better to use a battery charger on it, if it can't be fully recharged then it is faulty. Then the battery charging in the car checked with the DVM.

One question, does the charge fail light come on when you switch the ignition on, then go off after the engine is started?

[Poloobs]

Thanks for the reply.

I know asking here might not solve my issue 100% but I still post to see if anyone had similar issue and how they solve it.

Btw I don't see any charge fail light on dashboard.

I've checked the voltage with multimeter so here is the result:

I'm getting .575V when car not running. I know the battery is completely dead so this is expected.

I jump started the car and checked the voltage again and I'm getting 14.15V with just the dipped light on. This indicates the alternator is charging the battery or trying to?

Also, things I noticed: when I rotate the steering wheel, all the lights goes dimmer and engine feels like it's going to stall. And when I kept rotating the steering wheel, the engine died.

So any ideas what could be the issue?

I'm getting obd to check if it gives any error tomorrow.

[RUM4MO]

I think that that battery is now beyond recharging so replace it, either it was dying and is now dead or heavily discharging it has killed it, its ability to take on any useful level of charge have gone and its internal resistance as seen by the rest of the car will now be too high to allow it to provide enough current for starting and running the power steering.

Remember, the power steering in that car is the heaviest user of 12V current, even when everything has been sorted out, at idle if you demand steering assistance it will dim the lights etc a bit.

If you do not see the charge fail light with only the ignition on, then the alternator sense wiring under the car has failed and now needs fixing, in some circumstances these wires failing can cause no or undercharging which is going to limit the life span of the next battery.

Edit:- after getting that alternator sense/load wiring checked and repaired and a new battery, you will also need to monitor what the battery drain current is after the BCM has forced all necessary users to go to sleep, as a BCM S/W issue could be causing the continual draining of the battery as another reason why this battery is being flattened and killed.

[Poloobs]

I'll change the battery over the weekend and report here about results.

Btw, how do I monitor BCM. Would it be possible to check using OBD?

[RUM4MO]

You would need a VW Group specific scan tool to look at every smart controller.

The established way for checking for things like BCM not shutting down supplies is to monitor the overall battery drain when everything has or is meant to be asleep, then splitting up the powered sections to drill down into which group are causing trouble then splitting up that group, remembering that while one fuse might control the actions of a smart controller, it could well be another fuse that supplies the load current to its consumers, so things could get a bit confusing if you don't keep on top of what might be happening!

There is another method which involves accurately measuring the voltage drop across every in circuit fuse, VW Group do have a table, I think covering the expected values.

[Poloobs]

Changed the battery, car starts fine now.

But wherever I turn the steering wheel, it still feels like the car is going to stall. Feels like the car is going to stall wherever I turn the steering to get out of the junction.

I think there is something wrong with the steering electrical system. Don't think alternator has any issue as I've done the load check and the voltage is always above 13.4V with everything on.

Btw when I turn the ignition (not starting), I see the battery symbol on dashboard. It goes away when I start the car. That looks alright now.

Also, I've never noticed this before but shouldn't the car headlight turn off when the Switch is positioned at O. When the keys are in, the main beam headlight turns on when I have Switch is positioned at O.

[RUM4MO]

Headlights staying on while the engine is running could just be VW Group's early cheap way of providing DRLs, others with a similarly "DRL equipped" late 6R Polo might be able to confirm.

I think as said earlier, the old hydraulic/electric power steering system was a gross user/demander of electrical power, so while demanding large steering assistance, the alternator will be getting loaded up, and its "power" comes from the engine, so it drags the revs down a bit.

Edit:- good to hear that you have seen the charge failure warning coming on and going off, maybe after this horrible experience you are getting concerned about too many other things - that can happen and I don't blame you for that!

[Mabe]

Hi, I am new to the forum. My Polo is a 2015 (late 5th Gen, 6c) 1.2 (90bhp) TSI Bluemotion.
Yes the Daylight Running Lights are On all the time from the moment the engine starts.
On the subject of battery and alternator (hence car charging of the battery), I would like to post my recent experience and concern.
My car has an EFB type battery and (for me, the annoying) Stop/Start, which I disable every time I remember after each start.
After just over 4 years from new the car would not start recently. The small screen behind the steering wheel displayed, 'Low Battery, Charge by driving'. I disconnected and removed the battery to charge it outside the car. It had an open circuit voltage of 11.45V. I charged it overnight gently at about 13V but with a limit on the Current of about 0.8A. The next day I realized that with a small lamp load the voltage would keep dropping rather fast, so thought the battery had had it and bought a new replacement (I remember that at the last service I was told that the battery was not so good). It seems a life of 4 years for a stop/start battery is about standard.
The new battery had an open circuit voltage of 12.45V (about 80% charge according to some tables). The car started no problem and I went for a spin to further charge the battery, but also to check that things worked after power disconnection from the car's electronics. The only change I noticed was that the driver's window would not automatically continue up or down when the switch was released.
I was shocked that the on-circuit voltage after the run was 12.3V. Checking the Voltage at the battery terminals with the engine running at idle was about 12.8V. Accelerating to 2000 rpm did not make much difference. However I noticed on the DVM some sort of momentary flashes of around 13.6V, among the much more steady 12.8V (no consumer loads on. Charging voltage dropped slightly when aircon was briefly switched On). I am not sure how intelligent the car's charging is, and whether this is as it should be or not.
I shall keep monitoring the rested (24h) battery voltage and maybe get help for peace of mind.

[RUM4MO]

Yes, remember that these cars have smart charging which seems to mean that unless the battery is heavily discharged, very little charging will take place unless you are on the over run, ie engine braking, during which period, something like 13.9V or even more will get "crammed" into the battery.

My wife's August 2015 Polo 1.2TSI 110PS SEL still has its original EFB and I test it every year using a battery tester - it is still in good condition, just below its original CCA rating.

Edit:- monitoring the battery voltage using a DVM while driving it shows very low voltage readings unless on the over run.

[Mabe]

Thanks, that is reassuring.
This morning I arranged to have this specific matter tested. It goes in later this month.
I shall report outcome here for the benefit of all.
Monitoring the battery voltage while actually driving would be a good idea to do. I'm not sure if using the 12V socket in the car would be the same as connecting to the battery itself. I remember Maplin used to sell a small kit with a number of green, yellow and red LEDs to monitor precisely this.

[iichel]

The cigarette lighter socket should be fine.
Do you see any significant drops in voltage when you turn the steering? Like below 10v?

[RUM4MO]

The cigarette lighter socket should be fine.
Do you see any significant drops in voltage when you turn the steering? Like below 10v?

Iichel, the 6C Polo has an electric rack which does not cause the huge "power grabs" that you see in a 6R Polo with electrohydraulic power steering.

[Mabe]

This morning I wired a DVM to a Car DC plug with a view to seeing what voltages we got in the socket as we drove. We drove outbound a distance of about 25km (16 miles):

The minimum voltage while driving (accelerating) was about 12.8V. Curiously, at a time when we stopped with the engine idling, whenever we opened a door (either driver, passenger or both) the voltage rose to 13.2/13.3V. Closed the door and it went down to around 12.8 again. The courtesy light was manually Off, but switching it On hardly made a difference.

The voltage rose consistently and gradually to 14.7 – 14.9V every time I removed my foot from the accelerator pedal. Either when going down a hill, wanting to slow down or every time I changed gear. I see clearly what RUM4MO mentions about the overrun (engine breaking).

On our return trip home this evening, there was a slight change in that the more or less consistent voltage while accelerating was only about 12.2V all the way. Surprisingly low I thought. But again consistently, every time I took the foot off the accelerator the voltage rose (gradually, not instantaneously) to about 14.8V. I noted that it was very often that I took the foot off the accelerator – to change gear but also to slow down when approaching roundabouts etc. Again, when stopped on idle (12.2V), voltage would increase when a door was opened, this time by 1 volt to 13.2V. We used the air con, but switching it off did not seem to alter voltages much.

The most consistent aspect of the tests today was that always, when not accelerating, the voltage rose to peak at about 14.8V. Again when engine is braking. When just changing gear while driving, I may not have given time for the voltage to reach the 14.8V but could see it rising like to there all the same.

I cannot understand why the ‘accelerating’ (normal driving) voltage on our return this evening was so low, 12.2 Volts. I cannot see how that voltage could do any charging. The EFB battery is brand new and I would not expect it to be at that low voltage anyway. Maybe there’s some difference between the inside socket and the battery terminals, or maybe the battery was sufficiently charged already from the morning’s outbound trip.

When I got home and parked and switched off engine, I tested the voltage at the battery terminals. That was 12.53V.
So maybe we can be certain that a lot of the battery charging takes place when the engine is braking - something new to me, thanks. The test was worth doing just to see that happening. Yes checked once that steering made no difference. Sorry for long-winded post!

[RUM4MO]

You are correct the battery will not be getting recharged much in normal use unless it is discharged, it will only be getting "maintained" the alternator output will be getting kept high to serve all the users connected to the battery and in doing so avoids wasting fuel and raising emissions.

Also, when you check the voltage at idle you are checking the battery voltage while it is loaded, or in circuit with a load, all batteries have a finite internal resistance and it is that that eventually limits how much current can be removed from them.

When you switch off the engine, there will still be a significant load on the battery form controllers still being initially powered up and things like auxiliary water pump running, or even engine cooling fan, so measuring the voltage at switch will always give a lower voltage than if you measure it again after maybe 20 minutes, as by that time all unused controllers will have been forced to sleep.