By having the SRS system repaired. Time for a trip to the dealer. Do not attempt to repair yourself. Serious injury can occur. remember tho it is under warentee for life as long as you have not been in an accedent
Follow-up: I don't believe this is warrantied for life in my experience. Here's what causes this issue on Beetle side airbags:
The receiving side of the seat-belt buckle - the side where the metal buckle plugs in - has 2 thin wires going into its base on a plug. These activate the side air bags in a collision. There is a wiring harness under the seat which connect them to the side air bag. In non-collision situations, these tend to separate for the following reasons: 1. They are too flimsy and normal use makes them separate. 2. The wiring harness under the seat is too short. This means that when you access the back seat, which causes the bucket seats to lift up and lean forward, it puts stress on the wires, causing them to separate and the side airbag light to come on. I had one repaired by the dealer at a cost of about $400. I never use the back seat, but after the repair, the first time I pulled the seats back to clean the rear leather seats, the side airbag light came on again. It may have been the passenger seat that caused it this time. The original poster is right: You can't fix this by splicing the wires back together because of extremely narrow tolerances on the electrical impulses. In my car, the broken wires did not cause the airbag to deploy. I am guessing that there are other sensors that have to receive signals in a collision situation. The dealer charges about $100 just to diagnose the problem. The fix is to replace the receiving end of the buckle and the harness. In my case, I could see the broken wires separated from the tiny plug at the base of the drivers seat where it entered the seat belt base, but the wires can break internally where the damage can't be seen. VW has a analytical computer program called VAG which can diagnose this problem. If you don't want to go to a dealer, many German car repair shops have the software. it also works on Audi. This is different from a standard emissions OBII tester, which only checks emissions codes. You can buy the VAG software to use with a laptop, but as the original poster says, airbags aren't something for shade-tree mechanics to play with. This is just another example of VW problems that should have been subject to recall, but have not.