There is an increasingly common fault with the instrument cluster....it causes any/all of the following:
1. The back lights to flicker, and to stay on without the key in the ignition.
2. Dim warning lights that shouldn't be there. (there is no fault, just the light)
3. The revs/speedo/fuel/temp gauges to stutter, freeze or stop working.
4. The immobiliser to stop talking to the ECU, and then the car won't start! (Although once it has started,then for safety reasons it will continue to run no matter what the immo/cluster does)
There are companies that will repair the cluster for £150 ish if you send it off to them...You will not be able to start the car whiie it is away!
Another option is to buy a new one, £401 from SEAT!! plus you will need it coded to your car.
The third option is a secondhand one, (although it may well have the same fault) you will need the PIN from the old car, the PIN from your car and someone to code it for you. All in all a bit of a nightmare.
I have had this issue and it's caused by where the 2 connectors on the back of the cluster join the circuit board. Unfortunately there are about 40 pins on each socket, they are very close together , and they all need to be resoldered.
I also found this fault only occured in the winter, when the cluster gets cold at night. I believe the metal contracts with the cold, and that causes the bad solder joints to pull apart. If you remove the cluster, take it inside the house and warm it up, you will usually find that it will go back to working fine when you reinstall it.
Just be thankful that the dash cluster is about the only thing in the car that the spanish actually made! Luckily for us, the rest is straight out of the audi.