Bonsall, 22, was arrested early Friday by police who said they saw someone vomit out the passenger side window of his car. Asked how much he had to drink, Bonsall responded, "Plenty," then failed a roadside test.
Police said a blood test showed he had "excess alcohol content" but did not disclose the exact amount.
Bonsall, who lives in Boulder, starred as Andy Keaton for three seasons on the NBC sitcom in the late 1980s that helped launch the career of Michael J. Fox (search). Bonsall later appeared in episodes of "Star Trek: The Next Generation" and the 1993 film "Father Hood."
Bonsall was convicted of drunken driving in 2001 and his license was suspended, police said.