Horn doesnt work - 1998 GMC Sierra

Lift the hood of the truck. Locate the fuse box and lift the cover. Check the horn fuse listed on the cover of the fuse box. If the fuse is blown replace it. Have someone press the horn and listen for a faint click from the relay or swap the relay with another one with the same part number (IGN or AC) to test the relay. If you hear a faint click the horn switch on the steering wheel is good. If the horn works after swapping it with another, the relay is bad and you should order a new one. Remove the horn connector and check the voltage with a 12 volt lamp connected to the two wires or a volt meter when someone presses the horn switch. You can also directly wire the horn to the battery to see if it sounds. If it does not sound the horn is defective. If you do not have voltage check the black ground wire on the horn connector to see if it has zero ohms, or if you connect the 12 volt lamp from the black horn wire to the +12 of the battery the lamp should light. If not your ground wire is bad. I hope this helps you find your problem, but if you have any questions post a comment and I will answer your question.

Check relays and fuses. it may be time to change it.most cars have two horns inside. one with a low pitch and the other with a higher pitch. hope that helps!!!!!! :)