What happens to the co-signer if a car is repossessed?

The debt and repossession will become part of the co-signor's credit record.

The co-signer of any loan has the same financial obligations and liabilities as the primary borrower. They can be sued and have their wages garnished or bank account frozen. The co-signor has the same responsibilities as the signor. Since the cosigner generally has a better financial situation than the borrower, debt collectors tend to target the cosigner with aggressive debt collection strategies. This can include frequent telephone calls, letters, threats of legal action and damaging the cosigner's credit report as well as the borrower's.