Identify fuzzy black quarter sized spider with orange on abdomen, in Minnesota
This appears to be some species of jumping spider (family Salticidae). 


  [Note that] All jumping spiders have four pairs of eyes, with the anterior median pair being particularly large.


In particular, I believe your specimen is Phidippus audax (Bold Jumper). Specifically, I believe yours is a subadult bryantae variant of this species. 



 Source: David Hill 2014 

From Wikipedia:


  The average size of adults ranges from roughly 13–20 millimetres (0.51–0.79 in) in length. They are typically black with a pattern of spots and stripes on their abdomen and legs. Often these spots are orange-tinted in juveniles, turning white as the spider matures.



Your specimen shares the orange abdomen with connected black "splotches" that leave an orange triangular dot in the middle. Also, notice your specimen has two grey lines on the posterior cephalothorax as well as black/white striped legs. Finally, 20mm is close to the size of an American quarter (~24 mm).  


If you get a good look at the front of your specimen, you'll likely see that the chelicerae are an iridescent/metallic blue or green (a tell tale sign of this species and genus). 



 Source: David Hill 2014 



 More typical coloration (L) vs. bryantae variant (R). [Source: David Hill 2014]

P. audax tends to prefer relatively open areas to hunt and is commonly found in common in fields and grasslands, as well as on fences, exterior walls, and gardens. Finding one on your car, therefore, would not be so strange, especially given that they can jump 10-50x their own body length (Ruppert et al., 2004). 

Phidippus contains some of the larger species of jumping spiders in the family, and it is almost exclusively a North American genus. 


Specifically, P. audax is common in southeastern Canada, eastern and central United States and parts of northern Central America, and it has become increasingly common farther West. 






Citation:

Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 571–584