Also check your rotor while heating it with heat gun. My airhead would charge while running on 20-30 minute trips, but it was my first 300+ mile trip that the charging system slowly dropped it's voltage. Then it went back to charging after the trip. My system passed every test in the manual and on Snowbum's sight. So the only thing I could think of was to heat it with a heat gun while watching the resistence. Sure enough, the resistence went from around 3.5 and would slowly rise to infinity with more heat. I ended up going with the Enduralast system to run more heated gear, but this was an important part of trouble shooting my old system....HTH's.