Toyota 86520-01040 Horn Assy, Low Pitched

The horn for T100 models lives on the left side of the radiator. To check the horn works, first remove the electrical connection, then connect straight battery power to the terminals using two wire jumpers; replace the horn when it doesn't make a noise. Push the horn button to see if the terminal picks up voltage; if the terminal shows voltage but the horn still doesn't work, check your ground system. When the horn fails to work, you need to test the relay. Most horn relays come in two common designs: four-terminal or three-terminal, and either needs ground outside the relay unit. Check both sets of wires leading to the relay: voltage on one and connection from the relay to the fuse panel on the other. When both circuits show voltage, touch the horn button and look for a grounded path connecting the relay to the electronic horn component; a lack of connection means you need to find the broken wire, and if all wiring appears correct, replace the horn. After ensuring that the circuit links horn and relay correctly, look for either an open or a short throughout this path. To fix the horn, first disconnect the electric connector. Remove and replace the bracket bolt. Attach the bracket to your new horn. Reversing these steps will install your new horn.

If there's continuity to ground through the horn button, check for an open or short in the circuit from the relay to the horn.