I'm guessing you have A/C. If so you have a blower high speed relay mounted on top of the A/C suit case. It's likely stuck. Power to the relay coil is supplied through the ignition switch and should be disconnected when the key is off. You can eliminate it as the culprit by removing the inline fuse. Follow the 10 Ga orange/black wire from the relay you should find an inline fuse, it's probably in the firewall mounted wire duct. Remove the fuse, If the fan stops, replace the relay. The contacts can be fused or welded together. If the fan still runs or if you have heat only then the problem is probably the ignition switch. At the ignition switch you will find a 2 ga red wire and a 12 ga brown wire. When the ign is on the red, power from the battery, is connected to the brown wire. When the ign switch is off there should be no power on the brown wire. Check for voltage at the fuse block, A/C or HEAT fuse. Should be no power when the ign is off.
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