The Stovebolt Site Forums The Shop Area The Electrical Bay Heater blowing fuse - 1958 Chevy 3100 (original equipment)

I NEED YOUR THOUGHTS AND SUGGESTIONS. I’ve got a stock 1958 Chevy 3100 with all original equipment , I’ve got an original deluxe heater and original deluxe heater control switch. The wire to ignition switch to the heater switch has an old school inline 20 amp fuse . Every time heater fan motor is switched on, the fuse blows in one minute. Do I have a short circuit, or a fam motor pulling to much power or something else. Where should I start in tracking down the problem and what all and how should I problem solve the issue. Thanks for any advise. Pete