There is an electric exhaust fan with heater (fan,light,heater) in the bathroom. I noticed that when I switch on the heater that it sparks for a second when its first turned on, then there is a small glow at the end of a wire. I turned on the heater without turning on the light, it was dark, and I noticed it. Its an old unit. Is this normal or does it need to be replaced? Thanks.

Not normal and yes the heating element should be replaced if not the entire unit. The spare and glow is a significant hot or weak spot possibly caused by an accumulation of dust. The reason I said maybe replace the unit is because it is old. Parts may be difficult to find and a new unit runs about $50-75.