Jealous boyfriend decided to torch ex's car - but picked the wrong vehicle

A Dunedin man who tried to get back at his ex-girlfriend by torching her car made one obvious mistake, a court has heard.

The Toyota station wagon Michael Shane McFadyen, 27, set fire to actually belonged to the woman's mother.

The defendant had seen his former partner driving it and assumed it belonged to her.

McFadyen was sentenced to seven months' home detention when he was sentenced in the Dunedin District Court yesterday on the arson charge.

He and his friend Dylan Grant Woodley, 25, were talking about the failed relationship on the night of July 14 when they came up with the plan.

Woodley offered to set the vehicle alight, the court heard.

"Make it go boom," he said.

The pair bought petrol at a South Dunedin service station, before continuing to the victim's home in Abbotsford.

Judge Michael Crosbie said the actions were obviously premeditated.

Woodley filled an ice cream container with fuel, soaked a rag in it and put it under the engine. He ignited the rag and ran back to the car where McFadyen was waiting.

The bungled attempt at retribution was spotted by a member of the public, who called the fire service.

A passing motorist stopped to extinguish the blaze.

The Toyota was left with a burned front grille and damage to the bumper and radiator, police said.

The victim was particularly stung because McFadyen had previously stayed at her home and she had been kind to him in the past, she said.

The woman wrote in a statement that the defendant may have been justifiably upset with his daughter but was "disgusted" by his attempt at payback.

"A person's car is next to their home as probably the asset that people rely on most," Judge Michael Crosbie said.

"It's an asset when torched or burned ... leads to huge inconvenience."

Defence counsel Brian Kilkelly said his client now realised his actions were "quite unacceptable and appalling".

The judge accepted the defendant was now medicated for his mental health issues and held down a job.

If he received a positive report in three and a-half months, the judge said, he would convert the remainder of McFadyen's sentence to community detention and community work.

The defendant was ordered to pay the victim $750 for the emotional harm caused.

Woodley was sentenced in February to a year's imprisonment.