I'm building a prop controller for Halloween. The circuit I've designed has two relays controlled via transistors and a PWM motor controller via a mosfet.

The mosfet gate is tied to the pic via a 1K resistor. The motor and relays all have a 1N4001 tied between 12V and common. I’m using the same 12V supply for the motor, relays, and the rest of the circuit (5V regulator to the circuitry). The PWM controlled Fet is connected to a windshield wiper motor from a car.

The issue I'm running into is when the motor is run I am seeing spikes on the power buss.

Any thoughts on how to correct this issue without dramatically changing the design? I could drop optos in and use a separate power supplies but that would require a ton of rework.