It sounds to me your fan clutch is working and working well. I cleaned mine with a tooth brush and some electrical cleaner. I was trying to my mine come on earlier thinking the dirt would insulate the spring. On the older model P30's there may be 2 or three slots to insert the end of the spring to adjust when it will engage mine only had one slot. Your radiator if original my be partially blocked or just needs to be flushed, and the fan clutch is doing what it can to remove the heat. Your thermostat can be failing to open all the way and again you fan is working harder to compensate. I would check your radiator first, look for debris between the AC condenser and radiator look for bugs dirt build up on fins clean if necessary. Check thermostat in boiling water see if it opens a 1/4 in I have seen tstats open only 1/8 in right out of the box. Check you radiator for cold spots indicating a blockage. See what you delta T is from input to output of your radiator. Try the simple things first before you change the fan clutch.
