hi,
these cats were made by raymond and share many codes and common problems. when you replaced the lift pot and reassembled the handle you have the wires routed incorrectly and is more than likely jamming the horn button.this is why the tm, hd,hl and tm (hourmeters) are comming up.also when you install the lift pot you have to set pot voltage at apprx 4.45 volts....i am unsure of the code 12..good luck