Originally Posted by DennisMik (Post 9120055)

Fuse labeled RAD FAN 1 powers both fans on low speed.
Fuse labeled RAD FAN 2 powers both fans on high speed.

Originally Posted by DennisMik (Post 9120253)

I'm glad you checked the fuse. Based on what I originally posted above, it couldn't have been a fuse.



But that's because what I wrote is wrong for the 5th gen Maxima. It applies to the 4th gen Maxima (95 to 99).

What I should have wrote is:

Fuse labeled RAD FAN 1 powers Fan Motor 1 by the battery.
Fuse labeled RAD FAN 2 powers Fan Motor 2 towards the passenger side.

Sorry

Originally Posted by DennisMik (Post 9120055)

Fuse labeled RAD FAN 1 powers Fan Motor 1 by the battery.
Fuse labeled RAD FAN 2 powers Fan Motor 2 towards the passenger side.

Fan relay 1 makes both fans run on low speed.
Fan relay 2 makes the fan nearest the battery run on high speed.
Fan relay 3 makes the fan nearest the passenger side run on high speed.

When you turn the a/c on, both fans are supposed to run at low speed.

Personally, I think the problem is the fan motor. Check the electrical plug where the fan motor plugs into the car wiring harness. Make sure is is securely plugged together and that none of the connector pins have been pushed out.

Originally Posted by DennisMik (Post 9122491)

How are you determining that the fan is running at high speed? It will do that when the coolant temperature reaches 205º F, but at cold startup, the fan should run at low speed.

It may not be worth discussing because you have a bad fan on the driver's side. The two fans should always be spinning at the same speed. Replace it.

Originally Posted by maxinout93 (Post 9125730)

So both fans should run at the same speed high and low with the a.c. off?

Originally Posted by maxinout93 (Post 9125730)

My driver side fan spins faster than the passenger side fan on low speed. Which im assuming is making the driver side fan kick into high speed and run longer than normal if im correct?

Originally Posted by DennisMik (Post 9125739)

The design of the fan control circuit is such that the 2 fans run as one - at the same time and at the same speed. This applies to when the a/c is off as well as when the a/c is on. Whether the fans run at low speed or high speed is determined by the temperature of the water in the engine.



The reason the car has 2 fans is to have air moving through as much of the radiator as possible. One fan would be ideal, but since the shape of the radiator is rectangular, one big fan would stick up past the top and bottom edges of the radiator. So we ended up with 2 fans wired to work as one fan.

There is one wire coming from the ECU that tells the radiator fans to run at low speed. Because this one wire has to make 2 fans spin, the wire splits and goes to both fans. The same arrangement is duplicated for the high speed half of the radiator fan motors - one wire, 2 fans. This design does not allow the 2 fan motors to run at different speeds or times.

If humans have not been screwing up the wiring and/or installing wrong parts (specifically fan motors), the 2 fans will always run as if they were one - at the same time and at the same speed.

If someone has been cutting and splicing wires, and they don't say they have done this, we will be scratching our hemorrhoids until hell freezes over and still never figure it out over the internet.

If a motor has been replaced, was it the correct one? There are single speed fans out there in the replacement market. That single speed is no doubt faster than the Nissan motor low speed.

Another human screw-up is that Nissan used the same fan motor for the 4th and 5 gen Maximas. But they wired the plug different. It's the same plastic plug and you can install the fan motor in either the 4th or 5th gen Maxima. The different wire arrangement of the plug reverses what is low speed and high speed.

Maybe the fan motor that you think is running at high speed is really running at low speed and the fan motor that you think is running at low speed is really running much slower than it is supposed to. The armature inside the motor is mounted in Babbet bushings, not ball bearings. These bushings run out of lubrication and start to bind, slowing the armature revolution. The bushing starts to wear which allows the armature to wobble and that destroys the brushes and commutator. Check the fan. Spin the blade by hand and compare it to the other fan motor. Is it harder to turn? Also, can you wiggle the fan blade front to back? You should not be able to detect any play. Usually a bad motor makes more noise when it spins.