S60 Electrics: s60 2005-6 no charging

[5cilinder]

When i was driving , my speed and rpm dials went to zero.... and came back on
After stopping and restarting i got the no charging warning, the voltage dropped to 12ish volt with the engine running.

What can i check here ?

Pulley is ok and alternator is running
The ecm should have a connection with the alternator (lin bus) What voltage does it need to be?
Where is the ACM (alternator Control Module) or is it the internal voltage regulator?
Ill remove in the meantime the voltage regulator to measure it and the shaft sliprings

[XC70Bob]

The ACM is on the later version of the alternator it replaces the voltage regulator you normally find on an alternator and the earlier pre 2005 cars.

You can confirm which alternator you have by looking at the control wire.

Green with white trace is the later alternator with the ACM
Red with white trace is the earlier alternator with the older voltage regulator.

All the dials dropping to zero and then recovering sounds more like the problem the pre 2005 cars suffered were the instrument cluster suffered bad / failing solder joints, but I though they had solved this by late 2005 onwards.

[VOLVOBOY]

OP. If you only have a 12V charge it must be pulling the guts out of the battery so systems are stalling and recovering . Sounds very like the brushes and/or slip rings are worn to me.
Where did you take the voltage reading . At the battery or alternator ?
Best at the Alternator with engine running and as many things switched on as poss . Place one test-lead on Main Battery Cable terminal (by the fusebox) and other test-lead on body of Alternator . Should see 14 volts -ish DC . Then test at battery . Should see almost the same reading . If there is big difference could be bad earthing causing the problem .

[5cilinder]

-Connections and earthing is ok
-The linbus with the green/white wire is ecm controlled when the engine is running it gives 9 volts (i read somewhere that this is good? any confirmation?) it is used to energize the rotor to regulate the voltage and power trough the voltage regulator.
-The diodes are also ok
-Sliprings on the shaft have 3 ohms resistance seems also ok
-The voltage regulator itself have some short brushes and one is even shorter ...with little breakmarks at one edge.

-i think the voltage regulator is the culprit any resistance values on that one?
- i get on every combination possible open loop, it must be broken

If the stator brushes had gone bad will this give less sudden symptoms?

Maybe the last bit of brush broke of and caused a peak voltage that influenced the dials on the DIM?

[VOLVOBOY]

I think that if the slip-rings are not worn then you just need a new regulator .

[5cilinder]

I ordered one , tomorrow i will know for sure .
Everyone thanks for the thinking .

[5cilinder]

Replaced the voltage regultor everything is good again