The horns on my 84 944 never worked, the originals were cracked and coroded, and failed the hot wire test, so I replaced them but still no joy.
I tried swapping relays, and yet still, no loud noise when hitting the horn pad.

So yesterday, I read some guys first post on another 944 forum, and he said he had the same issue, and when he grounded the brown wire in the steering wheel, the horn worked.

Long story short, another ground wire to find, and clean, should get my horn working again.

Just thought I'd share,
Greg.

 

Mine required me to replace both horns and the relay. Now they work, but only when the steering wheel is straight. If I turn it more than a few degrees, they won't work.

One thing to check is the brown ground wire from the cross member to the steering rack. If that is missing or not making proper contact, the horns won't work.