check the voltage AT THE MAGNET. 12 volts minimum. Place one test terminal on each of the screws where the wires go in to the metal. If the clutch has slipped much it will be blue and warped and will never hold. We have in somecases bee able to take the cultch and magnets to a machine shop and reface true and have them work for years. On some machines a direct fused wire to an added relay has been necessary to quick fix the voltage problem. The wire from the header clutch now just engages the relay. Ususally problem only shows up when hot operating conditions. We have had some of the spring idlers let the belts slip that come off the clutch but the oly other area is the torque cam on the header drive shaft - the lH pulley to the right of where you hook up the header. There needs to be a 1_4 gap at slow speed here between the sheaves. Also welcome to the site! ask away and hang in there, sometimes takes a while to get answer.