Have you checked the fuses in the black box on top of the battery. Those steel like fuses.
Fuse 16 on the side of the dashboard.
When opening the cover it will be the 2nd fuse from the top left.
https://knigaproavto.ru/shemy/en/volkswagen/golf/97-volkswagen-golf-iv-bora-fuse-box-diagram-1999-2006.html
It is for the fan module. When the ignition is on and you pull it the fans should kick in and turn slow speed.
You can also put direct power by pulling the fan plugs and putting on power and ground to them. Fast speed and slow speed, fan should start turning.
https://forums.vwvortex.com/showthread.php?4448717-How-to-test-Rad-Fan-control-Module-or-have-fans-run-on-high=