If your 80A fuse is blown ...then you will not have any power at all. - even your door lights wont come on. This fuse is the mother of all fuse between your battery to your main electrical unit / fuse box (engine bay).
check if your door lights, parkers/headlights, horn and even hazard lights are still coming on. if they are not all working they you have no power from the battery. Check your battery aswell incase its flat due to a possible power cable that has been cut and shorting to the ground/stereo metal frame.
the yellow wire (if its from your stereo) is a + positive direct power. NO it will not affect the car from starting BUT if your battery is dead due to this wire grounding/shorting - then YES it will affect the car from starting (from the flat battery)... nomsayin?
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