Hi
this is not a pre-heater. This is the heating circuit of the O2 sensor pre catalytic converter… in cars they measure the o2 pre and post the catalytic converter, this allows them to determine the efficiency of the cat, and of course if it has been decat’d - i doubt the Pan-Am has post CAT sensors.. most bikes just have pre CAT sensors.. some (most) have it in the exhaust port of each cylinder but some use only one and they fot it in the section of exhaust after the pipes from each cylinder combine.. but that makes detecting issues with the individuals cylinder at fault more difficult
ok back to your issue.. the heating circuit either had 12v on it or not.. so might be a wiring issue - check wires for chaffing and check connectors
Hope it helps…