Motoraussetzer AFN 81kW | Posts 16+

Hi,

I'm not so sure about the "backwards flow," because, in my opinion, these are LEDs, not incandescent bulbs, and they only light up with the correct polarity.

I don't know how it was in your T3 from 1987, but at least my parents' gasoline Passat, also from 1987, had LEDs as indicators.

Best regards,

Jan.

Hello,

I'm not so sure about the 'reverse flow,' because, in my opinion, these are LEDs, not incandescent bulbs, and they only light up with the correct polarity.


You're probably right, but this is a simple matter to determine: if nothing moves on the valve, then what I wrote above doesn't apply.

That means the problem is likely located somewhere in the alternator or its grounding. Older T3 models sometimes have grounding issues, so I would start by investigating that.

Hello.
Wolfgang.

Hi Wolfgang,

I have a "real" incandescent bulb as a preheating lamp, not an LED. It was added later, because it was originally a gasoline engine. The preheating lamp is connected directly to the corresponding pin on the engine control unit (ECU) and then goes to ground. Or does the ECU switch it to ground? I'm not entirely sure about that, I'll have to check. So, a "back current" through the instrument cluster is ruled out.

Quote:

That means the problem is likely located somewhere in the alternator or its grounding. Older T3 models sometimes have grounding issues, so I would start by investigating that.

Why the alternator? The mass problem should rather be related to the control unit. And the battery is still there; the car sometimes runs even without the alternator. I haven't started looking yet, but I want to start as soon as my wife gets home by bus .
The weight distribution from the engine/transmission to the body should be fine, as I frequently remove and reinstall the transmission, so the relevant connections are often checked.

Regards,
Jens

Hello Jens,

The engine likely enters a temporary emergency mode because, at the same time, the charging control light illuminates and the turbo pressure drops.

Um, I was thinking of the red indicator light for load control, the one that's connected between terminal 15 and generator D+. If you meant something else, then you can disregard everything I've written above.
Does the tachometer now move when the light comes on?

Hello.
Wolfgang.

Hello Wolfgang,

"Argh, I meant the preheating lamp. What nonsense about the charging control lamp ."

Quote:

Does the tachometer now move when the light comes on?

No, not a bit.

I just bypassed the ignition switch and the wiring to the rear by directly applying 12V to the control unit (via a switch). The first test drive was without any interruptions .
It could very well be the ignition switch, so I'll need to bypass it directly tomorrow.

Regards,
Jens.

Hi,

It's not the ignition switch, because that's actually new, installed yesterday. Unfortunately, the effect is still there, and it feels even stronger than before .
"I've also noticed that the regulator for the alternator seems to be faulty. The voltage in the vehicle's electrical system is only around 13.0V with the engine running, regardless of the engine speed."
Well, there will be a new one tomorrow.
There are some wireworms around somehow .

Regards,
Jens.

Hello Jens,

In that context, it would also be interesting to know what happens when the onboard voltage is too high. Is there a specific error message for that? What voltage can the control unit still tolerate? Does it automatically shut down for safety reasons?

And by the way: There are also special regulators for the alternator that are used to charge the on-board battery. These regulators don't keep the on-board voltage constant either. I wonder if the control unit can handle that?

Hello.
Wolfgang.

Jens 16syncro wrote:

"Argh, I meant the preheating lamp. What nonsense about the charging control lamp

"
Hi Jens,

The light bulb turns on while the engine is about to turn off, which, in my opinion, is likely caused by a voltage drop at terminal 15 - if your EDC is wired the same way as in the AFN Golf 3, it will react exactly like that.

Hi,

The error has been located and fixed .
It was a loose connection on the starter motor, where terminal 30 of the alternator connects. This was also the cause of the low voltage in the vehicle's electrical system; the voltage regulator was not the problem.
I'm wondering why the battery voltage isn't sufficient to keep the motor running. Is it absolutely necessary to have a fully functional alternator?

Regards,
Jens.