What to do if I repaired a van for a customer but now they refuse to pick it up and pay for it?

To answer your question, the agreement you made with the customer needs to be reviewed. Any and all written documents, e.g. invoice, estimate, are important.  The dollar amount of the amount owed is a consideration.  I would review the applicability of Minnesota's Truth In Repairs Act to your legal problem with the customer: This law pertains to repairs costing more than $100 and less than $7,500.  In a situation such as yours it is certainly important to seek legal counsel with no delay as rights and obligations likely are affected by timeliness.