When should the fan come on?

I installed a new radiator in my dad's 91' LeSabre yesterday and while running the engine to get the coolant circulating, I noticed the cooling fan took a long while to kick on. The car isn't equipped with a temperature gauge so I can't say how hot the engine was until the fan kicked on.
Then, I turned the A/C on and the fan still didn't come on for about another 2minutes. Is this normal?:screwy: Every car I've seen ,including my 92' Park Ave, will automatically switch on the fan instantly after the A/C is turned on. I was just wondering if the system runs different in the 91' model or not. Thanks for the input!

225 degrees or when the ac pressures command their operation.