Nissan Repair: OVERHEATING, nissan maxima, light probe

Question
Hi Calvin,

I have a 1998 Nissan Maxima, my problem is that, the car is overheating, and the fans are not coming on.  I changed the thermal cooling switch, checked all the relays to make sure they work (interchanged the relays with other relays of the same voltage), but still its overheating. I haven't changed the thermostat yet and there is a small relay switch in front of the thermal cooling switch that I can't find out what its for.  What do you think is happening, and what is the smaller switch?

Answer
Hi Jon -

Have you checked the power to the fans? When the engine is calling for the fans to go on, check the terminals of the fans for power. Best thing to use is a 12V light probe circuit tester.

I would also replace the thermostat. If it is not opening, the coolant is not reaching the sensor, creating a false reading.

Hope this helps -
aloha
calvin