Customers at an east Brisbane Bunnings car park have been warned to check their cars are actually locked after a black spot of interference that renders remote mechanisms almost useless has been discovered.

Mike Ando, an energy efficiency assessor in the building industry and a former Beauty and the Geek contestant, said the "phase interference" appeared to be a quirk of building design in the area.

After seeing a Reddit thread about the phenomenon, he went to the Cannon Hill car park with his FUNcube Dongle Pro – a software-defined radio that could pick up radio frequencies from about 100kHz to 2.2GHz – and an antenna to get to the root of the problem.

"It only affects two or three car parks in that little area," he said.