'97 Max SE 5 spd. Actually, not ALL the time...they both turn on, simultaneously, approximately 30 seconds after my car is started...then, they don't turn off (unless the car is turned off). A little history: thermostat replaced w/ coolant flush...normal temp. gauge, car runs perfectly, A/C works perfectly, new coolant temp. sensor, checked/swapped all relays under hood, unplugged/blew out fan plugs. The local Nissan dealer is stumped, as is my local mechanic. Please help...I'd like to get this straightened out b4 I leave for a road trip (on Sunday). The air temperature today is approximately 85 deg F, if that helps. If I drive at highway speed for, say 10 miles, then pull over and check on the fans, they're both spinning and don't stop. This can't be normal. Thx in advance...

 

They turn on afer the coolant temperature reaches 200-205 IIRC.

Seems like a faulty sensor.

Hey, your car is running cooler!

 

A/C compressor on = fans on
Auto climate control set to AUTO will run your A/C compressor when temps are above freezing, which will also make the fans run.
If thats not whats going on, you may have a stuck relay or a faulty engine coolant temperature sensor.

The Haynes shop manual will help you trouble shoot your car.

 

Thx...as I mentioned in the initial post, I replaced the coolant temp. sensor (today, actually...made no difference) and the thermostat. Also, I'm aware of the fact that both fans run when the A/C is on. I've tried switching relays back and forth and, regardless of which relay is in place, both fans still run. Any other ideas, fellas?

 

There are two different temp sensors. One controls the ECU - that's the ECT sensor. The other controls the fans. I think it's the latter sensor you should check.

 

Really? Where exactly is the sensor that controls the fans located?

 

The ECT sensor sends a signal to the ECU telling it engine temperature.
The ECU turns the fans on and off depending on engine temp.

The other coolant temp sensor only operates the gauge in your dash.