1988 Subaru GL SPFI, Manual Transmission, Selective 4 wheel drive, has the lo-hi lever. There is a transistor under the Ignition Coil. The number on it is HF 8311. It looks like it is wired into the ignition coil. Do not understand it's purpose and could it cause a vehicle to stop running? My Subaru repair manuals don't go into this. thanks.