the cooling fan on my 2000 ac 400 runs all the time,my dad's 1998 454 the fan will only come on when the engine gets to a certian temperture.My question is,is mine working correctly,and if it is can it be modified to work like the 454,s does without any harmful side effects.Thanks.

yes your fan is working properly. I am sure you can add the temperature sensing unit to the fan. I think most people of they do anything just add an on/off switch for deep water crossings.