Jeff
Sorry - only just seen your post. This confused me on my Roadster: it's not a "heater fan on light" ... it's an "air conditioning on light". In highly-sophisticated Morgan fashion, the spare push switch on the dash (used for aircon - where fitted) is linked into the fan switch - so that it lights up when the switch is pressed in
and the fan is operating.
I thought my "fan warning light" had stopped functioning too - but one quick press of that switch, and there it was again

My guess is that you have the same issue. So before you strip the dash - apply the number one digit to the snowflake