Hazard lights not flashing with trailer connected

Hi,
It will be the 'flasher can' that needs to be replaced....was a problem with the early 100's although yours is not an 'early one' that's where the problem will be. :-)

The flasher relay (flasher can) is rated to a number of watts, this is the sum of the wattage of all the globes in the circuit. You have added more globes or watts by connecting the trailer, and probably exceeded the rating of the can, this will either slow it or stop it completely. Either reduce the wattage of some globes or replace the can with a higher rating.

Two straightforward solutions are available: Replace the flasher unit (there are flashers which function independently of the connected load) OR fit LED "bulbs" in the van/trailer as they present a far lower load than incandescent bulbs.

I forgot to mention: the failure of the hazard lights came on suddenly. Both a caravan and this trailer have been in use with this land cruiser for over 10 years without any issue. If it were an over wattage issue it would have been from the beginning I would have thought. That's why I suspected a fault and maybe the flasher can is the issue, but I'm not sure. Even my neighbouring trainee auto electricians are unsure.