Horn doesn't work and when trying, headlights turn off

[rrhonda87]

I'm pretty new to all this, I have an '87 V10 with LS swap. When hitting the horn button, it doesn't work. Maybe the bigger problem (or part of it) is the horn button will shut off the headlights when they're on. Has anyone had this problem or have ideas? Thanks

 

[Bextreme04]

... that has to be the weirdest electrical issue I've heard in a while

Those two systems shouldn't be linked in any way that I can think of... The newer squares like yours have the headlight wiring going through the turn signal switch, right? Maybe there is a short in the wiring in the column somewhere? Do you have cruise control with the LS swap? Are the cruise controls on the turn signal stalk? Since the horn button works by shorting the horn wire to ground, maybe you have a wire switched somewhere in the column when they did the swap and now it is shorting your headlight wires to ground when you hit the horn button?

 

[rrhonda87]

thanks for the feedback. No cruise. I'm replacing the steering wheel soon and wanted to pick some brains before opening it up.

 

[Bextreme04]

Is it a DBW or DBC LS swap.. sorry not pertinent to your problem, just curious. Either one becomes super easy to add cruise, although it is easiest with DBW, as you don't need a cruise control box.

For your problem I would suggest getting out a multimeter and start chasing wires. When you say your headlights stop working, do they just go off as long as the horn button is pressed? Does it blow a fuse?

 

[Grit dog]

Been a while since I tore into a steering column on an old Chevy, but thinking it's gotta be in the steering column since thats the only place the headlight wires get near the horn wires or contacts. I'd look for a wire going to the high beam/turn signal stalk that is shorted against something to do with the horn.

 

[MrMarty51]

Why not just clean the grounding wires between the rad support and the grounding wire, or, add another ground wire from the radiator support to the same grounding bolt as what the battery is attached to on the engine ?
Or at least try a jumper wire fron the rad support to the battery ground then see if everything functions as it should.