my horn on the 1988 f150 is out. the fuse was blown and i replaced it. now i just hear clicking when i press the horn button from under the dash. i have replaced the horns with a new one but that is not working. does anyone know where to start troubleshooting?

 

Howdy and welcome!

I am assuming you have cruse control?

Here is how the system works. There is constant 12volt power fed to the underdash relay you hear clicking. It is split between going to the switch in the relay that feeds the horn, and the coil in the relay that triggers the switch. When you press the horn pad, the coil is grounded out causing the relay switch to close (the click) and send 12volts to the horns.

Here are my horn tech pics...

Basicly look at the right side of my diagram to follow how it works.



The brown thing is the relay that was in a pain in the *** spot north of the gas pedal.



If I remember right, the yellow wire should have 12V all the time, and the either blue or yellow with green stripe should be hot when the horn button is pressed. I'll double check that tomarrow.

Here is where I actually ended up remounting the relays after my airhorn install for easy access.



Adrianspeeder

 

Thanks for the tech and pictures. The brown horn relay, is this what i should replace? What is the other black relay you show in your pics.

Thanks
Stan

 

The black relay is for controlling the air horns I added. Basicly a duplicate circuit of the stock system that I switch back and forth between.

Don't replace the relay just yet. You need to see where there is and isn't power. Use a meter or test light to check both yellow wires at the relay when the horn is pressed. If so, the relay is good and there is a break in the wire somewhere between the relay and horn.

Adrianspeeder