He was employed as a scout by Birmingham City, but acted as caretaker manager on two occasions. The first time was for three games between the departure of Dave Mackay and the arrival of Lou Macari in early 1991; Birmingham remained unbeaten under his management. After Macari walked out in June 1991 to join Stoke City, Coldwell again took over as caretaker, this time persuading most of the significant number of out-of-contract players to sign new contracts and not to follow Macari out of the club, and supervising pre-season training until the appointment of Terry Cooper in August 1991.
In April 1993 he replaced Len Ashurst as manager of Southern LeagueWeymouth. Unable to prevent relegation to the Southern Division, he stabilised the club and achieved a mid-table finish with a young side in the 1992–93 season, but was sacked in September 1993.