Can't speak to your Vanagon specifically.....  Do they use salt on the roads
in your part of British Columbia?  I've owned a number of Type 2 buses.
Their
usual problem was corrosion in the crimp/push-on connectors, probably as a
result of road salt.  This was both on the horn and on the connections to
the steering column outside tube.  If you have a friend (maybe a model RY
nut) who has soft-soldering skills and maybe a Dremel tool, enlist him/her.
Get rid of the connectors by soldering the wires to the lugs.  That
always eliminated my horn problems..... permanently.   Good luck!

Glenn McComas,  Queenstown, Maryland
87 Vanagon, 69 Baywindow, 87 vdp XJ6, plus some cars that actually run.