I've had this problem intermittently for the last year or so.  When I installed my Borgeson steering box I forgot to install the ground strap between the two halves of the new rag joint which I thought was causing the problem.  I remedied that error recently, but today was driving, used left turn signal to make a full 90 degree left turn and as I was doing that horn sounded and kept intermittently sounding.  I could sort of modulate it by adjusting the turn signal lever, but I ended up stopping and shutting engine off.  Was going to pull the horn's fuse, but couldn't remember which fuse goes to horn and it was night so I just drove home and didn't use turn signals at all.  No issues, but I won't drive it again till I resolve.  

I know I'll have to pull the wheel off and see what's going on in there, but was just curious if anyone has experienced anything similar and/or has any guesses as to what parts I'll need.  I'm thinking turn signal switch is going to get replaced for sure - it can be finicky at times with the canceling feature not always working right.  

 

I just installed a new steering column (Chinese import), and it did the same thing.  It was a defective turn signal switch in the steering column.  I had replaced one in the stock (non-tilt) steering column on my '75, which was not too bad a change -- the wired ran straight through and there was enough room for the flat plug to fit as well.  But on this new column the wire harness takes a confulated path and there was not enough room for the flat plug to fit, so I had to cut it off and resolder the contacts when it was all together.

When you pull the original turn signal switch, make sure you tie a sturdy string to the wires so you can pull the new one back through.  Mine got cut on the new column and I had a miserable time fishing another one through.

Thank you, Bill.  Going to replace the the turn signal switch and see where that takes me.  

 

Thank you, Bill.  Going to replace the the turn signal switch and see where that takes me.