Fan on at 240F ?

[cujotom]

Hi all... My 89 calais 2.3 quad 4 cooling fan wont kick on until just before the needle goes into the red, about 240F. It stays on briefly possibly cooling it down to 240F before it shuts back off. Shouldnt it come on before 240F. I just changed the thermo (To 180F for the summer), back flushed the system. Replaced both coolant temp sensors, (one for the gauge, and the one that the ECm reads off of to turn on the fan). If you turn on the AC the fan automatically turns on,(Although if you flip the switch to the defrost position the fan still comes on) I dont think it should do that on the defrost position. I mean to tell you touching that upper radiator hose, at 240F that hose is super hot! I just feel that maybe something isnt right with the fan kicking on that late and the fan running when its on defrost. Can someone give me some ideas? Should it be that hot? Also I changed all the relays around to see if it was that (No diffrence) Anyone help me on this one? Thanks Tom

[GTP Dad]

Make sure that you used the correct temp sensors and that the wires are connected properly to each one. A loose wire can cause problems. The ECM turns the fan on and it is not reading the temp correctly. If you used sealer on the threads and you used too much teflon tape it could cause the problem as well. Also make sure you got all the air out of the system. A small amount of air can get trapped at one of the sensors and cause the fan sensors not to read correctly until they get very hot.

As for the fans coming on when the defroster is on that is normal. The defroster actually causes the AC compressor to turn on because dry air clears a window much faster than warm air from the heater. So most manufacturers wire them this way. The fan coming on is perfectly normal for your car so don't worry about that.