Polo 6R 2010 - Power/Alternator trouble

[Dabon9]

Hi,

Today I got a problem with my Polo 1.2 diesel R6, First the battery lamp went on, then after 5 mins I lost the servo steering. So when I stopped the car I wasnt able to start it again, but after 1 hour it started just fine again, and eventually I wasnt able to start again.

So I measured the battery with the car running to 10.5V.

So my question is, is it absolutely sure that the alternator is the problem and is there any way to make that 100% sure.

And, is there any good guides to changing it on this car?

Thanks!

[iichel]

well you could measure the battery terminal voltage with the engine running.
you could also have a look at the fuses on top of the battery, special attention to the fuse where the black wire goes to. if this one is broken, the alternator could be fine yet the system is not charging.

[RUM4MO]

This happened to my daughter's late 2009 Ibiza 1.4 16V, and in that case the alternator was dead - actual fault unknown to me as I found it difficult to buy spare parts for it and bought a reconditioned one, same manufacturer, an official rebuild.

So, if it looks like everything else is okay, as suggested by iichel, and there is no output from the alternator, then it probably is a failed alternator - if you are unable to bench test that alternator and most of us do not have the facility to do that, then after checking what has been suggested you should either accept that that alternator has failed, or take the car to a garage for them to fix, there are few "100%" things in this world.

[Dabon9]

Thanks for your answers! Unfortunately no fuse was bad..
Do any of you know if an alternator with part code: 04C903023C
Will fit the 2010 polo? The part is from a 2014 polo

[iichel]

you'll roughly have two versions, alternator with LIN connection and alternator without.
best shot at a good match is to either look up by VIN and find latest version or recover part number of current alternator and find a good replacement

[RUM4MO]

One thing about this is, last night I checked on the ECP website (Euro Car Parts who is a UK based supplier of car parts), and I looked for the alternator details for an alternator for a 2010 1.2TDI Polo, then I looked for details for an alternator for a 2014 1.2TDI Polo, and both ECP stock numbers were the same, so over that period in time the alternators remained the same, but as iichel posted, you need the correct version as one is for the "no Stop/Start" and the other is for the "Stop/Start" fitted cars and both should be 140Amp max output rating. Also, it seems that the "no Stop/Start" version is rating as a nominal 12Volts output voltage whereas the "Stop/Start" version is rated as a 14Volt output voltage - this will be because the "Stop/Start" version uses "recuperative braking" to charge the battery, so the higher output voltage rating allows it to harvest more of the car's wasted energy during braking.

[veteran]

"........ it seems that the "no Stop/Start" version is rating as a nominal 12Volts output voltage whereas the "Stop/Start" version is rated as a 14Volt output voltage - this will be because the "Stop/Start" version uses "recuperative braking" to charge the battery, so the higher output voltage rating allows it to harvest more of the car's wasted energy during braking".

I don't think this is the case at all. Alternators for conventional non-Stop/Start batteries produce an on-load (ie. connected to the vehicle battery) voltage of around 13.8v when at the point of charging, though this statement has to be qualified by the precise charge state of the battery and the temperature. Without the alternator being at least that, the battery won't even begin to charge, whether from the alternator or anywhere else. The fact that some Start/Stop batteries happen to be labeled as "14v" has got little or nothing to do with recouperative braking; I think it's just poor, inappropriate labeling. Indeed, many vehicles don't have recouperative braking anyway, despite using Stop/Start. Mine, a recent 1.2 TSI, doesn't. So don't let that mislead you. I'd wager, in any event, that the amount of energy 'recovered from braking' and fed back into the battery is so small as to be of little assistance.

As far as I'm aware, there's no special requirement for Start/Stop batteries to have a charging voltage much in excess of 13.8v, though it's essential to not let the charging voltage (from any charging source) exceed about 14.8v. The latest breeds of bench-chargers ensure this, for example.

Dabon has a tricky problem on his hands. Finding out with 100% certainty why the on-load alternator output on his TDI is measuring only 10.5v isn't going to be easy, without using special kit. It might be that the battery is itself in such a poor state that it's actually dragging the alternator's output down. Without him going to the drastic lengths of buying a replacement alternator, therefore, it might be an idea in the meantime for him (I assume it's a 'he') to disconnect the battery (with the engine and ignition switched off, of course, and kept off until the experiment's over!) and measure the battery's off-load voltage. (To measure the battery's off-load voltage, you need only to disconnect its negative lead, ensuring that it's kept from making contact with any other metalwork in the engine compartment - but I repeat, do not have the engine running, or even the ignition on, while you do this). If, within about 30 mins it rises to 12v or above, then maybe there truly is an issue with the alternator and all that the battery needs is a jolly good charging up by using a suitable external charger? Don't ever start the engine with the battery disconnected, Dabon9, as otherwise you might permanently wreck a number of things. Even if the battery voltage is still low, however, that's not necessarily an indication that the battery is irrecoverable; with the right sort of bench charger, the battery might well be restorable.

If, in yourself, you're convinced that it's the alternator that's the problem, then I'd have thought that the easiest and least expensive action would be to go along to your VW dealer and buy a reconditioned one; as far as my knowledge goes, VW dealers sell them as replacements on the basis of exchange. You could then get either the dealer workshop to fit it, or you could fit it yourself (assuming you've the inclination, know-how, and all the requisite tools). Then, as far as the battery's concerned, you'd either have to bench-charge the one in the car before connecting it up, or you'd have to get yourself a new one. Or even go one better and buy yourself a decent bench-charger and thereafter keep your battery in a good state of charge!! Clearly, diesels make huge demands on batteries; all that glowplug current, every time you start up.

[iichel]

The start+stop/Bluemotion Technologies version of the alternator uses a LIN (local interconnect network) connection to the CAN gateway (where the battery regulator module lives as a virtual beast).

The story behind this, very short...
The LIN connection tells the alternator when to charge and how much to charge. This is part of the energy recuperation with regenerative braking.
The voltage AND amps that the alternator generates will depend on the power usage, the state of charge of the battery and the type of battery (EFB, AGM, regular lead).

Rough guideline:
1.2 TDI with start/stop --> alternator with LIN --> 03C903025F
1.2 TDI without start/stop --> 03F903023D

[veteran]

That may well stand for the stop/start scenario and for where the vehicle model actually uses recouperation (not all Start/Stop models do) but the charging voltage still isn't going to rise hugely, since it's fairly pointless to have it doing so, as the maximum end voltage that any automotive lead-acid battery can charge to is 6 cells at 2.25v each (unless the laws of physics got changed recently while I wasn't looking!). There'd be no point in trying to increase the charge voltage on a fully-charged battery, trying to force in more current than the battery can hold. In my view, there's really only one parameter of any great importance with an automotive alternator and that's the peak output current that it can deliver and it's that that's usually enscribed on the outside of it.

Perhaps it should be remembered that Dabon9's setup is a non-Stop/Start battery. I assume that, in 2010, 1.2 TDI's didn't use Stop/Start technology.

Incidentally, I'm no expert on batteries used for diesel engines but I've since wondered whether Dabon9 might have been measuring that 10.5v with the pre-ignition on. If that's the case, then he should repeat the measurement with the ignition key completely removed from the steering column.

Addendum: re-reading Dabon9's original statement, I'd say that the issue points more toward a battery fault than an alternator fault. One of the key things to be always checked when the dash charge light comes on is the tightness of the belt that drives the alternator; it might be slipping and allowing the battery to gradually get runned down. Or the battery might simply have reached the end of its useful life (become highly sulphated and perhaps beyond redemption). A conventional lead-acid one's only going to last for 3 or 4 years unless really well looked after.

[alexperkins]

My 2010 1.2 TDI had start stop

Its easy to tell anyway. If its start/stop the battery will be an AGM (or in some instances, an EFB) but both will be marked on the casing. Non start stop is standard lead acid.

[veteran]

My 2010 1.2 TDI had start stop.

Gosh, I'm surprised to learn that. I was assuming all along that Dabon's battery was a standard lead acid type. So, maybe he'll have to give additional consideration to his problem, if his is actually a Start/Stop battery? I must say we seem to be hearing a lot about apparently failing batteries recently.

Across the car industry, I think that readers will find that where recouperation is incorporated the battery type fitted is AGM, which can handle the small transient increases in charge voltage resulting from this energy recovery technique. Otherwise, the battery type fitted is EFB, and the charge voltage is clamped. The impression I've gained is that AGMs have in general been fitted to the higher performing cars, but perhaps in past years there have been some exceptions to that.

[iichel]

or you have to conclude that start/stop with energy recuperation is fitted into lower tier cars