Radiator fan runs continually

Woke up this morning to find the fan on my 1998 Plymouth Voyager (3.3-L engine) humming away at a high rate of speed. Pulled the 40-amp fuse to shut it down before it drained the battery. Now I have to start the van and insert the fan's fuse before driving. The fan is running at high speed. Ordered a used relay for $15 and will attempt to replace it when it arrives. If the relay is riveted to the frame (as I suspect it will be), what is the best way to remove it -- drill or angle iron? (I don't have an angle iron, but will add it to my tool bag if someone suggests it would be best for this job.) I'm really hoping that the fan relay is the problem. I'll post back here with the results.

Haven't had time to replace the relay yet -- cold weather. So I've been taking my van on short runs to the grocery store and such, knowing it would not have enough time to overheat. Yesterday, while on a longer run than usual, I heard the fan kick in, even though the fuse was pulled. When I got home, I lifted the hood, and sure enough, the fan was running. So my question is this: what does that 40-amp fuse control? The fan for the air conditioner?

The used relay I bought for $15 solved the problem. Fans now running properly, and the CEL is now clear. The relay was located in a difficult to access spot and took four hours to remove and replace. But -- problem solved!