For a couple quick hints;
If you turn the A/C on, the fans should come on. That'll check the basic operation of the high speed circuit & confirm the fans themselves are OK.
Then, the most common issue is low speed not working. That normally comes on first as it heats up, and in most circumstances does the job so it never gets to the HIGH temp needed to turn the high speed on. There is a resistor pack you can find between the fans (rectangular box with a four wire connector as I remember). The resistors inside can go bad, and the connector itself often gets "burned" from the power load especially with corrosion that's probably present at the age of the car. Both are replaceable & cause MOST of the "overheating" issues. The gauge & temp. readings get to the red & scary zone B4 the high speed kicks on if the low isn't working.... At that point the temp is rising quickly & the high speed has a chore to do to "catch" it and send the temps downwards again!
Manual would help on fuse & relay numbers (avail. on line if you don't have one), or one of our electrical experts may chime in who knows that info off hand...
Last edited by sailor; 01-28-2013 at 09:58 AM.