that's a common issue on this forum; surprised you haven't seen it.
It's the low-speed half of the Focus's 2-stage cooling fan. Removing it reduces your cooling system to a one-speed fan that kicks on with the A/C or when the engine is on a trajectory to overheating. Of course, if your old resistor was already rotted away (open-circuit), then the fan won't even realize that you removed it.
If you haven't noticed this already, then you will start seeing the temp gauge creep over to the 2 o'clock position when you're sitting in traffic, at which point the 2nd-stage fan will kick on and the needle will creep back to 12 o'clock.
The added heat stress over the life of the vehicle certainly won't make the engine any younger, but from what I gather, many (most??) old Foci are on the road and completely unaware that their resistor died ages ago. (me)
"I'm jealous of girls because they get to wear dresses." (Todd Flanders)