[Des]

This could be a relay at fault, power to fans via ignition controlled
relay, relay contacts have stuck together so now fans are powered always, not a
bad thing really, engine will get some heat soak preventing cooling once
stationary as cooling system will still have some thermo syphon effect,
this, and the nice blast of fresh air can only help prevent vapour lock
possibility. Disadvantages I can think of would be a flat battery if the fan
switch sticks on, or, in the event of an engine fire, could fan the flames.