Pontiac Repair: 1998 Sunfire Cooling Fan Not Running, coolant temp, fuse box

Question
I have a 1998 Sunfire with the 2.2L motor. I have what seems to be a fairly common sunfire problem, the cooling fan doesn't kick in. If I turn on the AC, it still won't kick in, which it always used to when I turned on the AC. Fuses are good and I took the relay to a parts store, they tested it and it was good. I took the relay out and jumpered the terminals with a paper clip and the fan started turning. Problem with that was there was a big spark, so I pulled the clip out right away, but the fan did start turning, so I don't think it is a bad fan, plus if I spin it by hand it spins real easy. I guess the only thing left that I can think of is the coolant sensor. Where is the coolant sensor and how can I test it? Or, is there anything else you can think of? When I'm idleing for a while, the temp starts going up and I need this fan to start working! Thanks!

Answer
Hey Bob:

Pretty good job of eliminating the different parts of the system. I would first off swap that relay with another one in the fuse box with the same part # and see if the fan works then. If not then start looking into it further. The coolant temp sesnor on that engine is either in the head or on the upper coolant pipe that attached to the head it has a connector on it with 2 wires. I don't know if I would condem that though. They RARELY go bad! I would lean more towards a wiring issue between the engine control module or a bad engine control module. Heres why. If the coolant temp sesnor was reading wrong you would more than likley have runing issues with this car. That sensor is a main input for fuel delivery. If the sensor was bad it would run bad cold due to giving the computer a wrong temp. If it were skewed low on the temp you would be using more fuel than normal as well. because it's telling the engine it's colder than it really is thus more fuel into the engine and MPG drop. What you really need is a scan tool so you can see what is going on here what the engine temp is reading VS the gauge on the dash if equipped and also a scan tool wil lshow you if the engine computer is commanding the fan relay on or not. Good luck :)