On 24 May 2015, a fire started in the roof void area of a bus and quickly spread destroying the bus. A forensic engineer’s examination of the bus revealed that the positive and negative electrical cables to the air conditioning unit fan were installed incorrectly. They were in a cross over configuration, which caused the two wires to fuse.

To reduce the risk of wires fusing, bus operators should have their buses inspected to ensure that positive and negative electrical cables are not installed in a cross over configuration.

This advice is effective immediately.

Approved by Stephen Turner, Director, Bus Safety.


The brand of air conditioner in this case was TRACS/CARRIER and we are aware that the source of the fire was within this unit. However we have no evidence to suggest that there was a fault with the unit itself. We therefore strongly recommend that the wiring within ALL externally mounted roof air conditioning units be inspected.

For more information about this matter, and/or bus safety legislative requirements in Victoria, please contact Andrew Chlebica, Manager Compliance and Information, on (03) 9655 6873.