[Ian M Davis]

Most things you describe suggests you are not getting enough power from the alternator except I am surprised that under those circumstances the battery has enough charge to crank the engine.

I think you must have 308 T7. A lot of 308s have battery charge status monitor. This is small box that sits on the negative terminal of the battery. It is probably this system that is detecting the charge problem. When this system detects a charge problem is load sheds - turns off non-essential electrical systems such as air-conditioning.

The car has an electric steering pump and the ABS or ESP braking system needs power from the battery/alternator as well. The first thing that needs to be checked is the battery voltage when the engine is running. The voltage should be about 12.7V when the engine is not running and 13.8 V when the engine is running.

 

[Ian M Davis]

Okay we appear to be dealing with two different cars here. I need both VINs to be sure I have the right car specifications but I have attached the starting diagrams for 308 T7 1.6HDi and 207 EP3. These diagrams show the alternator configuration. They both could be described as smart alternators but the 308 is more sophisticated. The yellow line (9049) that links between the alternator (1020) and the engine ECU (1320) is described as a "engine LIN bus". The equivalent line on the 207 (1085) is described as "alternator regulator control". Both lines control the alternator excitation.

Smart alternators can be commanded to stop charging in certain circumstances- some example:
When the engine is starting.
When engine needs extra power.

I think the best way to continue this is send me and RedSector a PM please let us know your VIN.

 

[Ian M Davis]

I have a Peugeot 308 1.6 e-HDI from 2012.

Are you sure about the year of manufacture of your car. As far as I can tell the 1.6eHDi is a 115PS engine which I can't find for the T7 but it is listed for the later T9. I found the engine designation on the online version of servicebox DV6C. I think the 308 1.6 eHDi has a reverse alternator. This system uses the alternator a starter motor in a stop-start system. I suspect your problem relates to the reverse alternator switching between the starter motor and alternator function. This discussion may be relevant: Energy Accumulator Fault P1A9C