Original Becker radio. When the car is running and the blower motor is on any speed but maximum, I am getting static while listening to AM radio stations. FM is fine and if the ignition is not running, the static on AM is reduced but not eliminated. I checked and cleaned all the ground connections that I could find. I also cleaned the battery terminals and cables. I disconnected the antenna cable and the static is still present. The static does not vary with engine speed. I removed the A/C controls and cleaned the fan speed switch. I was thinking that maybe the brushes within the blower motor could be wearing out, causing the static. I am trying to rule out all possibilities before I replace the radio. Any help that can be provided would be greatly appreciated