Authority member Rachel Larmer ruled Mr Bangs took sick leave to look after his family in circumstances where no one else was available to care for them.
It was ruled Mr Bangs informed his employer on each occasion, was open about it and shared medical information.
Mrs Johnstone told the authority other than his sick leave, Mr Bangs was a good employee and performed to the required standard.
The decision said Mrs Johnstone had given Mr Bangs two previous written warnings, one when he as well as his mother were in ICU and another when he called in sick himself, but then went to work at Mrs Johnstone's request - despite legitimately being ill.
Mrs Larmer ruled Mr Bangs' distress was significantly increased by Mrs Johnstone turning up unannounced at his home on August 12, 2016, after he took sick leave to look after a sick child.
He had resigned on August 2, but was working out his three-week notice period.
Ms Larmer said the visit appeared to be an attempt to "catch him out" because Mrs Johnstone asked where his wife was, why she was not looking after their child and asked to see the child herself.
Ms Larmer said another aggravating factor was Mr Bangs' manager called Mrs Bangs' work on August 16 to check she was there when Mr Bangs had to leave early to pick up a sick child.
Mrs Bangs was surprised to find Mrs Johnstone on the phone, who then quizzed her about her health, her children's health and why she could not have left work instead of her husband.
Mr Bangs said his dismissal caused him to lose his passion for being a mechanic which was something he had been passionate about since he was a teenager.
In addition to the $15,000, the authority ruled the parties had to agree to the amount of lost income Mr Bangs had suffered since leaving the dealership. Those details had not yet been made public.
The Rotorua Daily Post attempted to contact Mrs Johnstone. A woman called Sue answered the phone but when asked didn't confirm whether she was Sue Johnstone. The woman didn't respond to requests for comment.
Mr Bangs did not want to comment but his wife said both sides of the story were heard and she and her husband agreed with the decision.
- Rotorua Daily Post