You should be able to get the horn cap off of the steering wheel by turning it counterclockwise. My horn failed and I found that the horn wire going up the steering column to the horn button, switch, went bad. When you press the horn on the steering column you are supplying a chassis ground to the circuit. Testing with a meter should help you locate the problem.
2000 Monaco Diplomat 40PBD
2012 Grand Cherokee Limited
2008 FatBoy, three spoiled Great Danes and a cat.