1999 toyota corolla Horn doesn't work.

Did you have to remove the clock spring? If so makes sure you did crack it when reinstalling.

Should have a fuse box under drivers side dash and a fuse box under the hood. I think the horn fuse is under the dash on drivers side. usually 10 amp. I would get a test light and a friend and have the friend push the horn while i held the test light on the horn connector wires. It has two wires a voltage and a ground. If fuse is good but still no power at the horn then check the switch in the steering wheel. You could have a bad "clock spring" or steering wheel switch.

Check the horn relay to see if it works. Most cars use the same relays for multiple other functions. Check the part number on the horn relay and find another relay that is working that has the same part number. Swap out the horn relay with the known good relay. If that doesn't work, check all the wiring in association with the horn. If all the wiring is sound, then it is probably the horn itself, but that is very rarely the case.

You can replace the horn. Check to see if the wires connected to the horn have power. Check with a test light. If power is present then the horns are bad.

HI,
Try to find out first what is the part that cause the malfunction of the horn.
The three major part of the horn is the relay, harness & horn pad, and horn itself.
Check the relay if it is functioning by replacing it with similar type ( if you have the spare or a similar relay in the relay/fuse box in engine compartment ). Let somebody push the pad horn and if you hear a clicking sound on the relay, it means there is a current that activates the relay( no probs from the horn pad and harness ).
Check the horn, just get a wire and directly connect it to the positive pole of the battery and connect it( wire ) to the positive terminal of the horn, it should activate the horn, if not the problem is the horn and you have to replace it.

Hope that helps!

The horn relay is under the hood in the main fuse/relay box, remove the cover, the relay locations and fuses are marked on the inside.

10 amp fuse located under the hood on the drivers side fuse block........there is also a horn relay that is in that same fuse block.......if both of these are good get a test light and unplug the horn and get someone to hold the horn on while you check and see if you have power going to it.if you do then you know that the horn is bad and sometimes you can tap on it and get it to work......if you do not have any power and youknow for sure that the fuse and the relay are good then i would be checking the spiral cable. it is a ribbon that has wires in it and spins as the steering turns and the will break sometimes.......i would let a certified technician check this as it is part of the air bag system......good luck and i hope this info will help you......let me know or fixya know if i did my job and a thumbs up........thanks and if i can help you any further let me know i have been working on toyota and lexus for 25 yrs.................

check fuse then check relay or just check for power on the horn it self

If the horn works with direct connection, and fuse, relay, and circuit breaker are all good, it's the switch in the steering wheel. If it is anything like the chrysler auto's, the switch and the air bag module is all one unit, can't replace just the switch, the whole thing, and it's about $700 to $800 for those units, at least it is here, and can only get them at a dealer.

the horn is located behind the bumper, you will need a test light to test for voltage at teh horn connections, if there is 12 volts at horn connections, this means th horn is faulty.
if the horn is okay, check the horn relay - and if that is okay it could be the horn pad inside the car.
But it will most likely be the horn itself that is faulty.
Ask your local garage / mechanic if you are lost!!!