First thing I would do is check all the wiring. Check the ground in side the steering wheel and then check to see if you getting power to the horn with a 12 volt light tester or voltmeter. If you got a good ground and power to the horns then you know they are bad. Have hered you can take them apart and clean the contacts with some sand paper. Never tryed it though. Or you could get a used one or some place like B/EandA should have them new.
A simple way to check the horn is to jump the horn out just run a piece of wire from + side of battery and touch the spade connector on the horn as long as the horn is attached to the body it`s grounded. If it beeps obviously it`s good next thing I would check is the horn relay. Rockauto sells the low note horn for around $25,but I would check the parts for sale section here and at other forums first probably get it cheaper. Moparts is a good place to look.