I bought a running driving S70 today and had to get a battery for it(test drove with loaner battery). I get home and 18yr old son (his car to drive) hooks battery up backwards. Now as soon as I turn key over it blows 15 amp fuse labeled ignition. Any help would be appreciated but leaning towards new ECU. Thanks

 

What year is the car?

If that was my car I would figure out for sure what is shorted. Shorts are easy to find. The wiring diagram might be at volvowiringdiagrams.com. They have several years.