Heater blower always on full power

Hi there. I have a 1991 Brougham De Elegance. Whenever the ignition is switched on, the heater blower blows on full power, weather the heater is switchen on or off. I have put the problem down to the relay. Can anyone tell me where this relay is located, or is it down to a power module. If so, where is this module located?
Cheers,
James.

Blower power module on evaporator case underhood.