Mazda Repair Questions? Ask Mechanics for Answers ASAP
Hi There, I'm Clay a certified master automobile technician with 30 years of automotive repair and diagnostic experience.
The F21 horn fuse in the underhood fuse box supplies power to the brake lamp switch. Verify the fuse is good and there is power on the circuit. If the horn works there is a problem in the brake lamps circuit between the fuse and the switch. If the horn does not work the problem is with the fuse, fuse box or power from the battery to the fuse box.
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