The turn signal fuse isn't a "turn signal fuse" per se. It is actually the illumination control unit fuse.

This means that you have to check for short circuits on the following boxes:

* Illumination Control Module

* Console Switch Group (hazard and door lock switches)

* Body Control Module

According to the manual, the following units can't actually cause a short (because they're read in as a digital signal off the body control module):
* Turn Signal Multifunction Switch (the one on the steering column)

* Left Rear, Left Front, Right Front and Right Rear lamp assemblies.

My Jetta ALSO had a problem where the Fuel Pump fuse would blow all the time. It turned out that the problem was the O2 sensor shorting on the same circuit.

Good luck hunting this down. The best way to find out the problem is by looking at Service Manual page 8W-10 and 8W-44 and checking each element on the pathway to ground.

That 15A fuse blowing is a good thing, it means that the problem is easy to find. Don't lose hope and keep your head!