I have a 1995 Toyota Rav4 Jeep that the horn does not blow

An inoperative horn can be caused by a bad horn switch in your steering wheel, a broken "clock spring" under the steering wheel, a bad horn relay or fuse, a broken wire or a corroded ground ... or even the horn itself is broken. So, if your horn doesn't work, the fault could lie anywhere in the system. Here's one troubleshooting method.
Step 1: Check the horn fuse. Horns are located at the front of the vehicle and subject to water, road salt and grit. Over time, those elements can corrode the horn diaphragm or degrade the coil windings that cause the diaphragm to vibrate. That can short the power to ground and blow the fuse. If the fuse checks out, move to step 2.
Step 2: Locate the horn and disconnect the electrical connector. Connect one probe of a digital voltmeter to the electrical connector and the other probe to ground. Then actuate the horn. You should see battery voltage (12+VDC). If so, the horn button, any control modules, and relay are working and you have a bad horn. Confirm by attaching a fused jumper from battery positive to the horn. If the fuse blow, the horn is bad. If you don't see battery voltage at the horn connector, the problem could lie in the horn relay, control modules, horn switch, clock spring, or wiring harness. Of all those components, the horn relay has the highest failure rate.
Step 3: Test the horn relay. There are steps in this process. The easiest first step is to locate another relay in the fuse/relay center with the same part number and swap it in place of the horn relay. Then operate the horn. If it works, the horn relay was bad. Buy a replacement at an auto parts store or the dealer. If a replacement relay doesn't work, move on to the next test.
Using a digital voltmeter, remove the horn relay from it's socket. Check the socket terminals for battery power at the relay contacts and control coil (key on). If the control coil and contacts are getting power, next check for control coil ground when actuating the horn button. If you see ground, then you most likely have a wiring harness issue between the relay socket and the horn.
Step 4: If you don't get ground on the horn relay control coil when pressing the horn button, the problem could be a control module, clockspring, horn switch, or wiring harness issue...which are more of a challenge to diagnose .... meaning you need to take it to a repair shop.
Helpful?
Good luck with your troubleshooting!

The most common cause is that the ribbon contact drum under the steering wheel is faulty and has a broken filament. The part is called the "clock spring contact drum"