Actually all the cluster does in this circuit is house the warning lights and some diodes.

When the ignition key reaches Position II, the warning lights should come on, all five (battery, E-brake, oil, brakes and bulb failure, if I recall correctly). So OK, then what makes them turn off? I wondered and asked a helpful Volvo tech.

In Position II, sometimes called "Run" and sometimes called "Bulb Check", battery voltage flows to those warning lights and thence to a ground, and burnt out bulbs don't light.

The oil light grounds in the oil pressure sensor and goes out when oil pressure reaches some minimum pressure. The other lights are grounded through the alternator rotor windings via the brushes.

That small current through the brushes makes a small magnetic field on the rotor so that as the rotor begins to spin, electricity is created. When that happens, the dash lights have positive (+) voltage from the battery, and also (+) voltage from the alternator, so the lights go out.

Thus if the brushes are weak, or the wire connecting cluster to alternator is compromised, charging is affected.

Control of the alternator output is done by the voltage regulator, which is integral in the brushes unit. It senses the level of battery charge and raises the output voltage of the alternator as needed.

I can see it work by watching the voltmeter in my 1988 244GL. Higher voltage immediately after starting, and then dropping to normal after the battery charge used in starting is replaced.

Good Luck with your repair.

Bob

:>)