I approve of this idea. My box truck had the whimpiest little beeper ever when I got it - like a squeaky dog toy. CHinese-made air-powered is what I gave it. I don't use the horn much but when I do. HEH!
2nd button on the dash for the "meep meep" horn would be easiest. Plus if you just need to lay on the main horn, you don't have to wait for 2 seconds of meep meep.
Think you can help walk me through how to troubleshoot this? I'm not sure how to hook it up properly to get the gauge to work.
Three terminals on the top right are the oil gauge
C251 is the gauge side
Some potentially helpful background