The ignition switch has two dedicated terminals that ground through the ignition switch frame in the crank position. One terminal ties into the temperature warning lamp switch circuit and the other ties into the brake warning lamp circuit. After verifying that the cluster bulbs are, in fact, good and the Cluster Feed fuse in the fuse box is intact and passing current, use a test light clipped to B+ and probe the two GND terminals on the ignition switch to verify that each terminal actually grounds in the crank position. Repair accordingly.
The charge indicator lamp is controlled by the IC regulator internal to the alternator. Anytime the ignition is switched on with the engine not running the charge indicator lamp in the cluster will ground through the regulator via the dark brown wire connected to the #1 regulator terminal and illuminate. Again, using a test light clipped to ground and the ignition switched on with the engine not running, unplug the regulator connector and probe the brown wire connected to the #1 regulator terminal. If the test light illuminates dimly, the dash bulb should also be illuminated and its wiring from power through the bulb out to the alternator is intact and functioning. With the regulator connector still unplugged, probe the #1 regulator pin. If the test light illuminates normally, the regulator charge indicator circuit is functioning as it should.
The low oil pressure indicator lamp does not have a dedicated test function. Rather, it should illuminate anytime the ignition is switched on with the engine not running.