Had exact same problem.
Took some time but now horn(i got double from Audi) works great.
Ran one heavy gage wire from battery + to horn thru relay activated when
horn is pressed.
Added ground wire near horn location.
Leon
85 Subwagen

Tonya Pope wrote:

>Hi all,
>
>Have a problem with my horn.  I thought it was the mechanism (it
>had been sitting for awhile) so got a new one from the dealer.  The
>two wires get 12V between them when the horn is pressed.  When
>attached to a dangling horn mechanism, they get close to 12V
>(probably a matter of me not attaching the leads as good on the
>meter) and sounds like a sick duck, but works.  When I put it in
>place and tighten the nut holding it on, I only get about 6V across
>and all you hear is a thunk.
>
>What gives??  I'm trying to get it working by the time my failed
>insp. expires so that I can pass and continue to drive legally.
>
>Tonya
>87 Vanagon GL Wolfs
>
>
>
>