My 67 has a Heat Limit Switch that detects when the heater is over
temperature. If this switch is stuck in its tripped or over temperature
position, then the fan will stay on while 12vdc is applied to the
heater. I don't know what your reset switch does or how it would change
this stuck condition. Your heater also has a Fan Switch that causes the
fan to run for about a minute after the thermostat opens (room up to
temp). If this switch didn't open after the delay, this would cause the
problem. Does the fan go off after you do the reset switch thing? If
so, the problem is probably the fan switch.
Make sure you understand what the reset switch is doing. It may be an
addition by, or have modifications by, the PO.
Best Regards,
Jim