C4 alternator fault

[polophonic2025]

Hi all, I wonder if anyone could help me with a reversible alternator problem. C4 picasso 1.6ehdi stopstart 2013.
Car starts no problems, drives no problems and then reliably around 2minutes voltage drops from around 14.2V (lowest 13.8V highest 14.7V) to 12.8V (i.e. battery voltage). Illuminates error engine warning light, service light. After a few more minutes STOP and battery light - because the alternator no longer producing current. Turn ignition off, start car, back to normal until another 2 minutes.

Codes:
P1A84 PA19B

I guess the ECU is not getting what it wants from the alternator within some period of time after starting. This all points to bad alternator or perhaps bad voltage regulator in the alternator. But before I drop £1k on a new bloody alternator, I wanted to ask if anyone else had seen this problem and had any suggestions. Cheers!

[mickthemaverick]

You will find some information here which may help:

https://www.engine-codes.com/p1a84.html

[Sloppysod]

Hi, I can't find out anything regarding the fault code PA19B, did you use a generic diagnostic tool? It may be worth ticking some off the possibilities here.
https://www.quickstartcars.co.uk/knowle ... -explained

But rather than £1k, have you made enquires about getting it tested and repaired by a vehicle electric shop?

[PaulC5]

What happens if you put the headlights on, does the voltage then drop within 2 minutes ? If it is a smart alternator they reduce the voltage if the battery is charged up but if there is a high demand it goes back up. Only asking as there could be a battery fault.

[ozvtr]

C4 picasso 1.6ehdi stopstart 2013.

This is another start/stop failure.
By the sounds of it, I would suspect the start/stop ECU. The starter/alternators are relatively simple. These start/stop components are hideously expensive to replace, so you don't want to go about this willy-nilly. If you can't find any obviously damaged wiring or electrical connectors, then I would suggest that you "seek professional help".
The "alternator" does not have any rectifiers or regulator, the power management is done by the stop/start ECU.

[polophonic2025]

What happens if you put the headlights on, does the voltage then drop within 2 minutes ? If it is a smart alternator they reduce the voltage if the battery is charged up but if there is a high demand it goes back up. Only asking as there could be a battery fault.

Voltage remains constant - within a few tenths - irrespective of load. So lights, AC, etc... Battery was replaced about 6 months ago and has been behaving well.

[polophonic2025]

Hi, I can't find out anything regarding the fault code PA19B, did you use a generic diagnostic tool? It may be worth ticking some off the possibilities here.
https://www.quickstartcars.co.uk/knowle ... -explained

But rather than £1k, have you made enquires about getting it tested and repaired by a vehicle electric shop?

My mistake - the code is P1A9B!

[Sloppysod]

Yes that works. As you already know.

[polophonic2025]

Yes that works. As you already know.

At this point I'm thinking the problem is that the alternator is unable to regulate output, which the ECU registers and then stops it from producing current. Or, there is a nw/wire connectivity issue. In any event I need Diagbox to diagnose. Off to the dealers!