1998 Jetta TDI fuse #21

It turns out that the sunroof and interior lights are controlled by fuse number 21 which on my car was blown when I got it. I grabbed a replacement and the instant it touched its seat it blew again. The owners manual for the car says its "interior lights, power roof, clock" okay, lets start disconnecting things.

I pulled all the interior lights, and disconnected the power roof, tried another fuse and it popped again instantly. Strangely the clock still works, further research indicated that "clock" really means "analog clock" which I don't have, mine is a digital in the gauge cluster.

Well phooey, now I'm thinking maybe something from the aftermarket radio is shorting out because that doesn't work either so I start pulling the dash apart...

Note to self, research FIRST.

In the end great mother internet saved me. Not listed in the manual the central locking module is also run off fuse 21, it lives in the trunk on the mk3 Jetta.

Interestingly the module itself (its that brown topped thing in the picture) is very similar to the vacuum pump responsible for locking the doors on my '84 190D. I've got a spare for the 190D but the electrical connections are totally different. I found online a writeup for repairing the comfort control module for a Passat but it appears to not be the same thing. At some point I'll open mine up and have a look around inside. For now central locking is not all that important to me.

So now the sunroof and interior lights work, awesome but wait, now the headlights, wipers and washer don't work. BLAST! More research shows this is almost certainly caused by the ignition switch, not the lock part but the electric switch itself. Put one of those on the "to purchase" list.

Up next, removing human slime!