1997 Toyota 4Runner replacement horn doesn't work

Hi tlp32. Welcome to the forum. How many wires were on each old horn, and how many terminals on each new one? Do you hear a relay click when you press the horn button?

Caradiodoc

Hmm. Seems weird the plugs would be different on the two horns. Have a helper press the button, then measure the voltages on the four horn wires. On each one, one wire must have 12 volts and the other must have 0 volts. Leave the wires plugged in when you make the measurements. I'll look for the results tomorrow afternoon.

Caradiodoc

You actually do have four wires now.

"as instructed by the directions, attached the included wire to the mounting nut and the other end plugged onto the open terminal."

That's your fourth wire.

If you already have a test light, you can use that instead of buying a meter. If you have to buy something, there are a lot of inexpensive meters out there for under 5 bucks that work just fine. Look for a Harbor Freight tool store or something similar. Most of the traveling tool sales have the same thing and they really do work. If you go to someplace like Radio Shack or Sears, don't get suckered into buying a fancy auto-ranging meter or some other features you'll never use. You just need a basic voltmeter that will measure up to around 20 volts max. Most will go to 1000 volts on different scales but that isn't important for working on cars.

Caradiodoc

Hmm. Gotta have 12 volts to make the horn do its thing. Use a pair of jumper wires to connect one of the horns directly to the battery. It should squawk. That will prove the horn is not defective. As for the missing 12 volts, I suppose it is possible there is a second fuse for the horn current, but normally the same circuit is used that makes the relay click. On normal circuits, when the relay clicks, current travels from the battery positive to the horn fuse, to the relay, through the switching contact, through the bulkhead connector on or near the firewall, and to the horn connector. Somewhere along that path there is a break. If you can follow the wires according to their color, work your way back while measuring at various points. You're looking for that missing 12 volts.

Common suspects are corroded or broken wires at the connectors, (unlikely in this case as it would only affect one of the horns), a corroded connector pin at the bulkhead connector, or most likely, pitted relay contacts, particularly if one of the old horns was shorted and drew heavy current.

Caradiodoc