By the way its a 92 mk1 cabriolet
Well I would say that you don't have everything connected correctly.
There are no specific fuses for the Cluster, but they won't usually blow unless your battery is plugged in.
The Motometer Speedos are usually very reliable, so I would tend to think that you had a cable that was partially unclipped at the rear.
Follow this guide I will link you to, as it is the best way to make sure that your cluster is fine.
Remove your Instrument cluster: http://cabby-info.com/Files/DashRemoval.pdf On the back of your cluster, remove the Shroud off the main connector by pressing in the finger tabs, and carefully pry off. Carefully lift the Mylar connector off the tongue. Place one strip of electrical...
www.volkswagenownersclub.com
Get to know page (now it is 4) post 75 all things 1990ish Cabriolet in the FAQ's.
If you don't have a Bentley, or a Haynes manual I strongly urge you to get one.
Bentley is best, but Haynes has better copies of the Electrical diagrams (schematics).
Fist thing I would do is to follow the guide linked above to improve your connections to your cluster as that is the first suspect.
Then after it is totally re-connected, and the Battery is reconnected, then key in and in the run not start position, is all ok? yes good no, then verify that your 10V stabilizer is working.
If you don't disconnect your battery, and you turn on the Ignition switch without the Cluster connected your air bag lights will trip.
How do i reset those.... Get to know the FAQ's and or Cabby-info.com.
Airbag System
DVOM (Digital Volt Ohm Meter) on the 20V dc scale.
10V stabiliser is the big looking transistor that is sitting all by itself at the top left of the cluster as it sits in the car.
The middle leg is ground, and the other 2 legs are Battery, and about 9v-10V
So measure from the middle leg to each of the others, is this correct?
If you are missing a voltage, then I would suggest that in the guide that I linked above you verify that pin 14 black has Battery voltage on it to frame, and Battery to pin 2 ground brown, if those voltages are correct then that pin 2 (ohms scale or continuity checker) to frame should ring or be @ 0 ohms (smallest scale for your meter (Ohms).
I have had over the years the pin 14 mylar become delaminated from the mylar and that buy pushing on and off the connector it would scoot up and not make contact.