1991 ford f150 wont start when fuse that goes to the heater is in but if u pull that fuse out it fires right up. When the fuse is in it cranks once then everything dies lights on dash, head lamp ect.
Sounds like the blower is bad. Try to disconnect blower first with the fuse in, 2 doesn't work short at fuse or the fuse box. TEST battery and alternator . check one of these should help you.
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