Unfortunately the insane engineers found a solution where there was no problem. Instead of the horn switch turning on the ten-dollar relay to blow the horn, the horn switch now sends a voltage to the most intelligent computer on the car, the instrument cluster, which interprets that and sends a digital signal to the FEM, (Front Electronic Module), which turns on the horn relay. That's right; two computers involved in blowing the horn. The typical repair bill for a dead horn is between $700.00 and $800.00. I hope to hear your bill is much less. The dealer will have to diagnose the problem. You've already done all you can with your dandy observation that the relay, fuse, and horns are okay.
If I had that circuit in my car, I'd be modifying it to work with the simple switch and relay like all cars had in the past. There's no need for this Rube Goldberg system. This isn't just a Ford thing. Most manufacturers are doing the same types of things to purposely make cars unnecessarily complicated and cost us way too much to diagnose and repair.
Thursday, September 29th, 2011 AT 12:47 AM