I have a 1990 F150 the Horn only works with the key off when I turn it on NO horn .

 

I have the same issue with a 1989 F150. I took a jumper wire and grounded the steering wheel insert/horn button and the horn worked with the engine running. Based on that I believe it to be an issue with the steering column not being grounded.....or some kind of connection issue. A Ford mechanic told me it was the clock spring, but it does not appear to have a clock spring....so I am curious to see what kind of solutions are posted here.

 

I know this is an old thread, but has anyone figured this out?