Hello RR boffins,
I recently had an alternator fail and saw all of the modules/computers shutting down as the battery limped us home.
its a 2012 4.4 V8 Diesel.
After fitting the new alternator, the car runs perfectly, charge is at very steady 13.4v under all loads, but after running for 20-30 seconds, I get the charging system fault indicator on the dash.
It disappears each time I restart the car and comes back shortly after.
No engine light, just red asterisk and battery symbol on the dash.

It does not seem to log any codes, unlike when the alternator failed when it logged the DTC and instantly put the car into restricted performance mode before the engine was running.

I believe this tells me that the sense wire is ok, just not sure why the delay and alert.

I have now also noticed that the seat fans immediately stop once the warning comes up on the dash. Everything else still seems perfect.

Has me very confused.

Was it a Denso alternator you fitted?

Yes, Denso alternator

Charging voltage should be more like 14.8v

OK, Update.
16hr drive and the voltage was locked on at 13.4v

Checked the earth - all good
NO voltage between negative battery terminal and engine block.
checked fuses - all ok

Disconnected Negative battery terminal for 2 hrs. - no difference.

the ONLY system that is not functional when the charging fault shows is the heated/cooled seats.
Everything else works.

Any ideas why the new alternator is only charging at 13.4v ? Is this software controlled ?

Yes the alternator is software controlled.

It may discharge when at a steady speed or accelerating and charge hard when decelerating

I think it works a bit like a hybrid car by recovering braking into the battery.

So your charge should not be at a steady 13.4v

You could try telling the car it has a new battery fitted.

can this be done without a plug in tool?

otherwise, I will have to organise a visit to the specialist.

Needs a tool.

The Gap IID Tool is a good investment