double check fuse 21, take it out and physically check it with a multimeter. if its ok, then you prob have a dead dash or burned wiring.
check the wire to pin 13 of the dash, goes to U2/1. unfortunately VW decided to make all the dash wires white in the mk3 which makes your job hard. also look at the black jumper block above the fusebox, and the wire from there to E/2 and D/8.
next check the plug on the speedo sensor, should have ign live across the black and brown wires. if that checks out then locate the blue jumper block above the fusebox, and look for burnt out wiring there, also check wire from fusebox pin U1/22 to dash clock pin 27, and also look at the white/bluue wire to pin G/11.
see my fusebox faq in the mk2 maintenance section for info on the pins, there are pictures of the fusebox in there too but its been rejigged a few times so the order is a little messed up
