Intermittent connection! But where?

Hello everyone,
'On my Passat, manufactured in July 2000, the lighting for the instrument cluster, climate control, radio, etc., intermittently turns off and then back on.'
I initially thought it might be the switch or dimmer, but adjusting it or pressing it didn't have any effect.
The funny thing about this error is that sometimes only the illumination of the instrument cluster doesn't work, and then the illumination of the climate control system fails. Then again, absolutely nothing happens.

Can anyone give me a tip, or tell me where I might be able to find something?

Best regards, Harald.

Hello, the only possible solution would be: from the light source, connect the blue wire (pin 5) to the blue pin (pin 20) on the fixture connector. Run a cable to bypass the wiring distribution box; if necessary, also check the 12-pin connector on the air conditioning unit, pin 5 (green/blue). If there's no improvement, the light switch is likely defective. Best regards, Oliver Volk.