But with money tight at the Worcestershire club, Kidderminster have slumped to bottom position in League Two.
Youth-team manager Shaun Cunnington had been appointed caretaker manager, assisted by Gary Barnett.
Youngjohns said: "Both Jan and ourselves are united in our disappointment at the league position the club currently finds itself in - results haven't gone the way we would have hoped and Jan's task has been made all the more difficult by the horrendous injury problems we have suffered.
"The club needs a spark to re-ignite our season and Jan felt it would be best if someone else tried to do that. It was a difficult decision for him but we respect and understand his rationale."