In general automotive relays aren't upto the job of switching inductive loads like motors.

Applications Considerations
In some applications, the contacts may be subjected to punishing current
surges which can drastically reduce their life. Consider an incandescent
lamp. A 40 watt, 120V AC lamp has a current rating of .33 ampere. The
resistance of the filament when cold, however, is so low that initial inrush
current may be as much as 6 amps! To attempt to switch the 40 watt
lamp with, say 2 amp contacts will result in early contact failure.
The same situation exists in motor and transformer applications, and in
applications where significant distributed line capacitance exists. During
start-up, a motor can pull 600% or more of its running current. Thus, a 3
amp motor may actually pull 18 amps or more during start-up. A contact
rated at least 20 amps should be used. Additionally, when disconnected,
a motor acts as a voltage generator as it slows to a stop. Depending on
the motor, it can feed back into the circuit voltages well in excess of
rated line voltage. These voltages appearing across the separating
contacts can cause a destructive arc to exist between the contacts, which
can lead to early failure of the contacts. Because of this, it is desirable to
suppress the arc.