Palazzo Not Charging from Engine Alternator

I also had the Trombetta problem. The contacts were coated with a black carbon like substance that I thought was the plastic case material migrating to the contacts. My conclusion was too much heat. The 12V Trombetta has more than 20 watts coil power and almost too hot to touch. I found a White Rodgers 15V coil unit with 200 amp silver contacts but about 8 watts coil dissipation. About same price as the trombetta. White Rodgers recommends using it for this application. So after more than two years still working perfect. Google White Rodgers 200 amp solenoid to find the part number. By the way I was able to clean the non working Trombetta contacts and it worked! Now a hopefully never needed spare.