VW 109 Power Supply Relay - Jetta, Golf, Passat. VW Power Supply Relays are just a heavy duty switch that allows a little bit of electricity to control something that needs a lot of electricity. This relay is for the Power Supply, and if it fails, it can make the whole car quit just like someone turned off the key. This relay is usually referred to as the VW "109" relay because of the relay manufacturers number printed on the top of it. It is not the actual VW part number.
If you have replace or tested your VW power supply relay, and you are still having problems, check the ignition switch next. This is the electrical portion, not the key tumbler. Also inspect your fuse box for a short circuit or water damage, or you may be chasing electrical gremlins for longer than you had hoped.