Is this the time for a new alternator or not?

[Palatinux]

My 22yo alternator failed after the rainy a stormy days of storm Ciarán.
 

Normally the battery light goes on while making contact, and it should go out after a second or one/two after starting the car.
This time the battery light stayed on and I measured 12.17v on the cigarette lighter > alternator not working, so I shut off the car.

30 min later the alternator was working again at 14.2v, but the voltage dropped to 13.90v when my lights where on. 13.75v with the blower at 2500rpm (it's been that way for many years).

I measured the voltage drop between the alternator > battery (pos and ground) on all major locations, which are the same including the battery itself: 0,06v on the pos, and 0,01v on the grnd, 0,07v together, which is nearly perfect.
No AC voltage, but if you measure around 2/2,2x the DC voltage in AC, try reversing the polarity with your multi-meter. If it then reads 0V, then the alternator is ok, but you're meter is budget ( I noticed)

I charged the battery at home at 14.4v and the charge amp dropped under 2A within 5 minutes (battery nearly full) to 0.5A after around 20/30 min. When I stressed the battery with a 55W 12V lamp for 5 minutes, the battery voltage eventually goes back to 12.56V after some rest. So the battery seems OK too even after 6 years of use (I use an additional max 120ma cigarette lighter solar panel in the car to keep the battery charged all the time because normally it's out after 3/4 years).

From what I understand: To keep a full battery (float) charged or to charge a battery to 80% (not fully), you'll need a voltage between 13.5 and 13.8v.
To fully charge a battery to 100%, you'll need a voltage between 14.2v-14.5v. 14.6v an higher will eventually boil your battery (gassing voltage). 14.2-14.4v is the sweetspot.
 

From my prospective, it seems that the original ( 047903015Q ) 70A Bosch alternator / regulator has issues maintaining the right voltages since it easily plummets voltage under load compared to the baseline voltage w/o load. Some say this is normal, but I assume this is on full load otherwise you can replace the battery every two/three years. Last time, a few years ago, it dropped to 12.9v under full load.

In the old days, the 2-wire (one-way) signal-load from the alternator informed the ECU about it's load, resulted in a slightly higher stationary RPM when I switched on the rear window heater when stationary. But I haven't noticed this for many years.

 

Lets take a look at the alternator itself. This oldy was serviced in 2017 with new bearings, a cheap Chinese 'Transpo' regulator, by a 'specialist' that found it necessary to solder the statorwires to the plate so I cannot remove the protective cap of the sliprings to service them, evenly vile off the copper sliprings (that's ok), replace the Philips screws of the regulator with some weird size bolts, which only can be taken out with a special or thin socket wrench. So I had to drill them out which gone terribly wrong... but I already expected trouble ahead and it needed to be checked at this moment. Back in 2017 I'd gone back twice to that specialist because the voltage was dropping too much in my opinion... he said that the alternator was OK after testing it on a bench.

What i  also found there were crooked voltage regulator brushes, though even worn. And one of the two sliprings had regular wear, while the other had none, though fully blackened (scratches are from a screwdriver). In my opinion, one of the brushes did almost no job, but I'm not sure anymore what is considered to be 'normal' anymore.

So I hope someone with more experience can inform me and maybe other with similar issues. The info online is often inconclusive, and I still have a feeling that the 'specialist' was gaslighting me to avoid his responsibility / warranty back then.
 

[Breezy_Pete]

8 minutes ago, Palatinux said:

I measured the voltage drop between the alternator > battery (pos and ground) on all major locations, which are the same including the battery itself: 0,06v on the pos, and 0,01v on the grnd, 0,07v together, which is nearly perfect.

With how much electrical load on the system at the time of these measurements? 

 

[Palatinux]

Hmm. Indeed Pete... No additional load on the system at that time. But a few years ago, I connected some jumper cables directly from the alt+ to the bat+, and from the alt-(bracket) to the bat-. That didn't make any change on the voltage on high load. But I would not surprise me if a new alternator won't fix the problem and I've cleaned the contacts too a few years ago.

As for the two DFM wires; are these two only to inform the ECU or can the ECU also control the voltage?

 

Edited 9 November, 2023 by Palatinux

[Breezy_Pete]

49 minutes ago, Palatinux said:

No additional load on the system at that time

Try it again when the system is loaded enough that the voltage measured across the battery terminals is well under 14.2V, then repeat the voltage drop measurements. 

It will be interesting to see if the total of the voltage drops on each connection plus battery voltage add up to 14.2V or not.

 

One of the small wires (the blue one) is the alternator excitation, only used for monitoring the output voltage after its initial function of booting up the alternator. It is self generated after this, once alt is spinning enough.

The other is DFM, which is just information to the engine ECU about how much the alternator is 'trying' (the duty cycle of the regulator).

 

Output voltage is fixed at the alternator +ve output terminal by the regulator, as long as the current demand is less than it is capable of supplying at that engine speed and full duty cycle.

 

 

[Palatinux]

1 hour ago, Breezy_Pete said:

Try it again

Thank you Pete. I've already ordered a new alternator (Dynamo Volkswagen 70A 305.526.070.010 PlusLine) that will arrive tomorrow because this one is not trustworthy or serviceable anymore. An alternator is replaceable, but your 'men's best friend' is not.

But I'll do a proper testing sequence soon when I have enough time to focus.

That is useful information about the two wires. What is the correct workflow of the battery light on the dash? contact on > battery light on > engine starts > alternator starts > regulator modulates the voltage over the blue wire > ECU sees regulator is working > ECU turns off battery light?

[Breezy_Pete]

Sounds like a good description of battery light function except it's the onboard supply control unit (often called BCM on later cars) that supplies initial blue wire current and monitors voltage, not engine ECU. 

 

It then tells instrument cluster electronics via CAN data what is going on, and instrument cluster switches battery light LED off/on as necessary.

 

When the new alternator is fitted, check voltages/volt drops with load applied to make sure that a bad connection or crimp joint hasn't developed since your jump lead experiment.

Edited 9 November, 2023 by Breezy_Pete

[Palatinux]

That makes more sense indeed.

I had planned to take the BCM apart anyway because the relay of the internal lights is sometimes buzzing when I just sat in my car (for 3 min) with cold/damp weather. But the days before the storm, I already had a wet carpet for the first time on the driver and passenger side. Reforming and lubricating the seals was not enough, so I also had to align the 4 door catchers with their central markings.

Since my old alternator had dried up completely, I've noticed this green/grey rust (red arrow) on the windings of the stator. Which is a good indication that the insulation lacquer is failing on these windings. You may not notice anything when measuring the resistance on the sliprings or during dry and warm weather. But when it starts to rain, the windings might short-circuit which causes a drop in power during load or complete failure.

I've already received an alternator yesterday, but tats was the wrong part and I recommend to check PN on the old alternator before ordering. I hope the new one will arrive today, because I need my car.

Here is a good video btw to completely service my and the wrong ordered model, which are quite alike. https://www.youtube.com/watch?v=Pk7F8ERd-KY

 

[Palatinux]

The new and right 70A alternator is now placed and tested. Not much difference in the voltage drops, but this new alternator provides a much more stable voltage when switching loads. Normally, the reading light was dimming a lot when switching loads and now the front lights don't even dim anymore while using the power-assisted-steering while parking in... and I've never seen that before since I bought the car in 2006

It's still unclear for me what was going on with the old alternator, but I think replacing it completely was a good decision instead of only servicing it (cleaning and a new regulator). Hopefully someone can confirm or deny my earlier findings for others who may have a similar issues, so we all know what to look for.

What I do know now, is that I was mislead by the so called alternator revision specialist in 2017, since he could have seen this on his testbench.

The voltage drop readings will be in the next post.
 

Edited 11 November, 2023 by Palatinux

[Palatinux]

I'll do some better measurements later on after cleaning almost all the contacts, wires, fuse contacts etc. again, plus I will apply additionally soldering on the wire <> connector contacts even if they are clean and in a good condition. It's better to waste my time on that, instead on fault finding in the future on this old car while it's raining cats and dogs again.

During half load (dim, front, ventilation, rear heating), I measured the following drop voltages between the alternator and the battery:
+0.15V, -0.04V - 14,22v alternator voltage, 14,02v battery, 13,77v internal voltage through cigarette lighter.

During full load, which is half-load plus side-mirror heating, high beams, fog-lights front and rear, while blasting 'Raining Blood' through the speakers and the subwoofer:
+0.14V, -0.04V - 12,05v internal voltage through cigarette lighter.

I see some room for improvement, but it's still just under the 0.2v at 0,19v lost.

[Breezy_Pete]

Pretty good; I guess the 0.15V is on the positive wire path? Thinner than the earth wire I think, so natural for it to be a bit higher, but could be improved I think.

 

I guess that was all with engine just idling?

The fact that full load had same volt drops on the cable paths to battery as half load suggests the alternator was already maxxing out on current at half system load and idle revs, probably.

Everything should be good when driving around with higher belt speeds and more current capability from alt. 🙂

 

 

 

 

[Palatinux]

Yes, the loss is 0.15V on the positive wire path between the alternator and the battery during half and full load. That wire should be 25mm2 according to the manual and I guess the length is 1.5m.
So if you have 13.8v, you should expect a drop of 0.06v at 70A at just the wire, excluding the drop on multiple contacts (4x-6x 0.01v?). You can always pull another cable to the battery-box from B2 if required.

Reving up the engine to 2000rpm did not made a lot of change on the voltage during one short load-test. Which is quite concerning to me and I expect some design flaw is also in place.

I've already noticed in 2017 that soaking most of the contacts and wires first with soda (dissolve aluminum oxide), then soaking with cleaning vinegar and scrub it with a toothbrush (dissolve copper oxide), rinse with water then alcohol (de-grease) and lastly applying solder on top of the wires, made a huge improvement back then. So, I'm going to try this again and share my findings for this quite common issue on my cars.

[Palatinux]

Today I finished cleaning all major positive contacts, cables and fuses and got a 0.10v improvement in the measured voltages but only 0.02v improvement on the voltage drops. Especially the positive junctions above the relays near the steering wheel needed some cleaning and tightening. Same goes for the relay contacts.

I also took the BCM apart, en didn't see any broken connections. And the buzzing relay is still there... somewhere... Maybe it's a relay in the Comfort Convenience Module or CCM. And that's for another time.

While scanning all the modules in my car, I got a "17911 - Load Signal from Alternator Term. DF: Implausible signal - P1503 Intermittent.

* I measured 11.02v and 11.22 on the DFM and L1 at the alternator, so the wires are fine.
* In vagcom, at "Engine" > "Measure blocks" > block "053", I see a load of 30% when the engine is off and it goes all over the place when the engine is running.

So I assume this "70A 305.526.070.010 PlusLine" alternator has a bad or incompatible regulator.

 

[Palatinux]

P.S, I made a post in 2017 about the old alternator, and the L and DFM voltages are still the same now as back then. The load was reported correctly even in the VAGCOM logs. I hope I still can get a new alternator that will meet the OEM specs of the 047903015Q.

"* The two signal cables (L1 and DFM) at the alternator read 11.5v from the car with the contact on (not running) and the signal cables and connectors look good. Battery light stays off when the alt. signal connector is disconnected when on contact > ok "
 

Here are some pics of my BCM in case anyone need them (if they have issues with L1). Including some pics of the relaybox and positive connections in front of it.