Parking brake lamp stays off if lever pulled

I have a 1991 XJ. I swapped the Bendix ABS to ZJ brake booster some years ago.

The "brake warning lamp" on upper left is illuminated while starting the engine but it stays off when i pull the handbrake lever. Unfortunately i only have a 1994 FSM so the wiring diagrams could be a little different to my 1991 Cherokee.

I did several tests with my voltmeter. The "parking brake switch" works and i have continuity on the wiring from the switch to the main body connector on the lower left to the instrument panel.
Unplugging the telltale connector on the instrument cluster my voltmeter shows 12V on pin8 while ignition start and lamp is illuminating. Following the 1994 wiring diagrams Pin4 must be ground while ignition start. While ignition RUN there is a low voltage below 1V on pin8 but there is 12V voltage on pin4 which must be ground while ignition start. Telltale connectors description says pin4 is "ignition fuse 'd' ". Now i am confused because the ignition switch must switch the voltage on the "brake lamp indicator" in two different directions on the pins8/4 on my instrument cluster.

Anyone an idea how to make the brake warning lamp illuminating when the hand brake lever is pulled?

The brake lamp circuit is a switched ground. In the run position, the circuit should show 12v all the way to the open switch.

The "bulb check" function of the ignition switch grounds the circuit in the start position to verify the bulb is working so you know that portion of the circuit is functional.

so all you have left is the circuit from the bulb to the switch to verify.

test the circuit by grounding the connector at the switch. the lamp should light when the key is the run position.