Cooling fan wire problem



Hi there,

I purchased a Nissan Quest 97 that needed a new cooling fan. The problem is that there is not a connector coming from the relay box, just the 3 wires (ground, low and hi - black, white with blue stripe and white with red stripe) and I just purchased a new cooling fan at local auto parts store that has also 3 wires (black, green and red). What wires should I connect together? What it would happen if a miss place the wires?


Carlos Rudge


It would be very helpful to get a wiring diagram. That will identify the original wires. You may be able to get such a diagram online at Autozone. Go here: and click on Repair Information. A Haynes or Chilton’s book, available at any auto parts store, should also have the diagram.

If you do not have a diagram, test the original wires as follows. Clip the wires and expose the copper. Attach a voltmeter to a wire and to a ground. Run the engine so that the cooling fan would normally come on and read the voltage. The colored wire that shows 12v is the high speed wire. The other colored wire should show less, perhaps 9v. If both wires show 12v, you need to guess whether the car wants to be running the fan at high or low speed and which wire is active. (A/C on or off?) Black is ground.

On the new fan, the black is assumed ground. There ought to be instructions about the red and green wires. If not, measure each colored wire for resistance to ground. The wire showing lower resistance will be for the high speed connection. If resistances are the same, they are interchangeable.


There is not a wiring diagram for your mini-van at autozone. I looked.
The black wire is ground. From the wiring diagram, the two power wires should both have 12 volts. The low speed side of the fan motor should have a higher electrical resistance (ohms) than the high speed side. It’s possibly opposite. Anyway, hook them up one way, and turn on the A/C (ignition key ON). If the fan runs high speed, it’s connected correctly; if not, reverse the wires, and try again.


Both the high and low speeds of the fan motor tie to 12 volts power. The fan speed is determined by the coils in the motor. I suspect that the low speed wire on the new motor is the green wire and that should tie to the wht/blu wire and the hi-speed will tie to the red colored wires.


And you were concerned about misconnecting the wires. In that case the fan would operate on high when you were expecting low speed. Nothing worse than that should happen. Fuses protect the circuits.


Usually the positive wires are the thickest.


Hi there and thanks. Here is the update: I’ve got the multi-meter and found the following on the new fan: green: 3.2 ohms and red: 1.6 ohms. (NOW I know that green is low speed and red is high) On the other hand I turned the car ON and the put the A/C also and every time the A/C cranked (every 30 sec for the period of 5 sec each) one of the wires from the relay was energized (12v - 14v) and the car never warmed up enough to energize the other one. (The gauge was in the middle and never got any warmer than that, even with the A/C on). Am I supposed to see the same wire kicking 12 -14v in even without the A/C on? (Because it did not) and when the other wire is supposed to come up and under which voltage?

Thanks for your knowledge.

Carlos Rudge