A 1998 Cadillac Deville does not have a blower relay. The system has a fuse and a controller to feed power to the blower motor.
might need to replace blower motor
bad blower motor
The blower motor relay on a 1980 Cadillac Coupe Deville is situated on the passenger side. It is located in the vicinity of the firewall and is just below the windshield.
Probably the blower motor, wiring to it or control switch
On the fire wall. Behind the engine.
Defective Blower Motor Resistor Pack.
the blower motor is located on the passenger side of the interior under the glovebox.
In the motor.
With that year deville...its more than likely the blower motor
The blower motors only work with the engine running. If the blower motor has three wires on the electrical plug, then the blower motor module is built into the unit & it's very expensive. Sometimes, you can tap on the motor with a hammer & it may work or slowly turn. If this is the case, replace the blower motor.
The blower motor fuse protects the blower motor electrical circuit. The blower motor relay operates only the high speed function of the blower motor. The blower motor speed resistor operates the lower speed functions of the blower motor.