Insurers are urging car buyers in New Zealand to look for signs of water damage and to check a written-off register before agreeing a deal.

The country has recently been struck by unprecedented flooding on the North Island, followed by destructive Cyclone Gabrielle.

Waka Kotahi NZ Transport Agency’s register recently added 524 vehicles as write-offs with a water damage annotation.

Water can corrode electrical and mechanical components, causing failures that take weeks to become apparent. Problems can affect many vehicle systems, including those related to safety.

"Until they are properly repaired and certified as such, flooded vehicles pose a safety risk, which is why insurers write them off in the first instance," Insurance Council of New Zealand Te Kāhui Inihua o Aotearoa (ICNZ) CEO Tim Grafton said.

When writing them off, insurers deregister them as water damaged write-offs then dispose of them through salvage companies, he said.

The ICNZ says while insurers act responsibly to get water damaged vehicles written-off and deregistered, there is “no robust system” to ensure the safety of flood-affected uninsured vehicles. Owners of such vehicles should take them to be inspected by qualified experts.

Water damaged write-offs must be inspected, repaired and then certified by Waka Kotahi-approved agents before they can be re-registered and put back on the road.

“Unfortunately, some owners may try to sell water damaged vehicles that they’ve tried to fix themselves, without using properly qualified experts,” ICNZ said.

The ICNZ recommends a professional independent pre-purchase inspection specifically addressing water damage concerns.

Warning signs can include a musty smell, damp carpet, excessive condensation, mould or mildew, water line marks, silt in crevices, irregular noises or faults such as flickering lights, having to jiggle the ignition key to start the vehicle, and corrosion or oxidation on metal components.