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My HVAC fan suddenly went to high with switch off. It stays on high while car is running. Never changed/tested a relay before. Any help?
Using a ohm meter (usually a setting on a volt meter), test prongs 86 and 85. If it read open, it is bad. Or take a 9 volt battery and hook it to these terminals. If you hear a click, it is good. If not, the relay is bad.