Horn going off when braking
 

Afternoon,All
I am the new owner of a 99 express passenger van. Everything works great except in the last day, when I apply the brakes, the horn goes off, loudly. Was working on it today and noticed that even when ignition is off, if I pulled on wires or bounced on the drivers side the horn went off. Seems like it's shorting out and triggering the horn.
Anyone ever experienced this or any clue how to fix this problem? Thanks for any feedback.

Was there an aftermarket alarm installed or removed? Trace the horn circuit if you can....

Horn issue
 

I've owned a lot of Chevy vans over the years. I've had 4 Express vans. Wiring issues can be tricky. I'll bet there's a pinched or upbraided wire in a wire harness. To troubleshoot this issue you'll have to trace the wire back from the horn. A service manual can be helpful. Most manuals, like Chilton's for example, have wire diagrams. If you disassemble any wire harnesses, be careful to re-wrap them. Typically there's a corrugated, split plastic tube that's wrapped around these harnesses to protect them. If you find wires that are not protected (maybe somebody who previously worked on it took off the protective tubing and didn't put it back on) I'd suggest buying and re-wrapping the wires with the protective tubing. The tubing is readily available at most auto parts stores and comes in a variety of sizes and colors. Check the wires, especially the wire that you're tracing, for nicks, scrapes or abrasions in the insulation. Repairs to wires can be made with electrical tape, however this isn't going to be adequate in an area of the vehicle (like the engine compartment) that'll be exposed to water. I've used a combination of silicon and electrical tape to make repairs, but it's pretty messy. Shrink wrap is a good solution if you have a heat gun and you'll need to cut and splice the wire back together. There are waterproof splice connectors that can be sealed up with a heat gun. The connector is wrapped in shrink wrap that shrinks and seals when heat is applied. Another issue to look out for is that wire harnesses are secured and kept away from hot or moving parts. For example, if a wire harness comes loose and comes in contact with the exhaust manifold, it would melt and make a real mess. Or if it came in contact with the belt or any pulleys, that would damage it too. Zip ties work good to secure wires. Troubleshooting automotive electrical can be pretty involved and time consuming. Depending on the time you have, you might want to have a mechanic take a look at it. I hope that helps.

Thanks for the responses. Seems there is a short in the wiring harness right behind air intake causing I to contact the body and triggering the alarm. Hope this is it. We shall see

Sorry, I don't have any advice other than to second an option above. I just had to comment because I've had a bad day, or a couple of days and.. well.. I read your title and started laughing! I'm sorry for your problem, but it just seems rather funny to me to envision you driving down the street with the horn honking as you apply the brakes.

Good luck, when it's fixed I hope you laugh too.