Ok, I need to get this horn fixed to pass TX safety inspection. I can hear the relay under the dash working, but the horn is silent. Are there any possibilities other than just tracing and testing the wires to the horns?

 

Common points of failure is what I'm asking about, FWIW

 

Year and model....

 

Ahh, sorry. '88 GXL coupe. But I already found it by stealing the horn CPU from my '87 TII project car.

Are there any other common points of failure?

 

Installing temp wires from battery to horn, to isolate if you have a wire issue. Direct power

 

As you already found out, its the horn cpu that is the common failure point. Mostly anything having to do with electronic components is a failure point on these cars : P (true story by the way).

 

At the largest plug in the CPU if you jumpered the Green/White wire to the Green/Red wire it should cause the horns to sound off. The G/W wire should have constant voltage on it. When the horn button on the steering wheel is depressed the horn switch puts a ground on the Green/Orange wire in the large plug at the CPU. If the first test causes the horn to work then you could stab a wire into the back of the G/O wire location in the plug and ground the other end of the jumper wire to a "suitable" ground and the horn should sound.

 

It could also be an issue with the fuse.