Radiator fan - why four wires instead of two ?

[Grossel]

Hi.

Same car as discussed here:

Wire designation on complex coloring schemes (Nissan 2000)

Hi. I'm helping a friend that have a Nissan x-trail from 2001 with an electrical issue. We suspect there may be some fault to the actual wiring itself (car have be subjected to rough treatment some years back). In order to help myself to locate the fault, I make a schematic (my own, that only...

www.electro-tech-online.com

So, we took out the radiator fan because we initially taught it was dead. However, I managed to get it to run by using a small simple 12V transformer+rectifier (doesn't immediately broke if shorted, and too little maximum current to kill the fan motor).

But the question is why car manufacturer seems to put four wires to a fan? The measured resistance between each wire is too low to determine anything, therefore I tested on bench.
The test results yields the following observed result (omitting all test resulting in running in opposite direction).

See table below (I'm somehow not able to put cursor after table, so the table have to come last)

I also measured the voltage between the poles not used when fan was fed by two wires, i.e. while fan running for second last line in table, I measured just above 2.5VDC between black and blue (the weak transformer only manage to output ~6V to the fan running).

Because I doesn't have tested with a proper PSU yet, I'm not sure if the fan is fed using all four wires (like in last row) using a proper 12V supply will simply cause the fan to run faster (because the weak transformer itself is the main limiting factor). But then again why waste an extra wire if it turn out 3 wires should be enough ?

black wire	Yellow wire	Green wire	Blu wire	Result (does it run)
negative	nc	nc	plus	runs ok
negative	nc	plus	nc	runs ok
negative	plus	nc	nc	No running. Near short (around 2 ohms)
nc	negative	nc	plus	runs ok
nc	negative	plus	nc	runs ok
negative	negative	plus	plus	runs ok

 

[atferrari]

Risking yo say something ridiculous, one of those inputs, could it be an input for PWM signal as in PCs fans?

 

[Diver300]

A lot of car fans run a various speeds. One way of doing that is to have several brushes and they are connected ind different ways to give different speeds.

Unless you have a really powerful supply and some way of measuring the speeds, you may not be able to tell which connections are giving faster and slower speeds.

This thread (https://www.electro-tech-online.com...-wiper-motor-circuit-this-complicated.164779/) was about two speed wiper motors, which are often achieved by having three brushes.

 

[picbits]

On a car fan I've just been using on a project, one wire was for a PWM signal at 100Hz (ish) for speed control and it had a second for an analog input also to control speed. Not sure on the Nissan ones but you will probably find it has some kind of speed control on it. Are all four wires the same gauge ?

 

[Diver300]

Car fans can be up to 1 kW, so they would take about 80 A. Your "near short" of 2 Ohms would give about 6 A with the motor stalled, and it might be a combination that is used in the the car.

Some fans are controlled by LIN, but the ones that I have seen like that need a valid LIN signal to work, and they have two huge wires and one or two tiny ones.

 

[Grossel]

This paricular fan have four wires having same dimensions. There are no pwm signal wires on those fans.

 

[Diver300]

This paricular fan have four wires having same dimensions. There are no pwm signal wires on those fans.

I think that each wire connects to a brush, and that in the car they are connected in different ways to get two or more speeds. I suggest that spin the fan by hand, measure the voltages, and tell us what you find.

The voltages will be quite small as you won't get it anywhere near full speed, but how much bigger one voltage is than another could be quite informative.

 

[Grossel]

The voltages will be quite small as you won't get it anywhere near full speed, but how much bigger one voltage is than another could be quite informative.

OK, I just get this tested as best as possible using two separate multimeter, fan is manually spin in forward direction:
Green - Black : 475mV
Yellow - Blue : 461mV
Also given all the factors making measurement error such as my fingers doesn't hit button accurately within same millisecond and how different multimeters behaves under erratic DC voltage, I'll say it seems those voltages are pretty equal.

 

[Diver300]

OK, I just get this tested as best as possible using two separate multimeter, fan is manually spin in forward direction:
Green - Black : 475mV
Yellow - Blue : 461mV
Also given all the factors making measurement error such as my fingers doesn't hit button accurately within same millisecond and how different multimeters behaves under erratic DC voltage, I'll say it seems those voltages are pretty equal.

OK, but what is the voltage for Green to Yellow? The fan runs with power on green and yellow so there must be a connection.

 

[Grossel]

OK, but what is the voltage for Green to Yellow?

Yes - this lays about 0,6-0,7 spinning by hand, about same as for green-black and yellow-blue : but I haven't tested this with 3 separate voltmeters.

[edit]
I know milliohmmeters may not be of much use on a DC motor with brushes because the value fluctuates when turning (even very slowly) and and also when not rotating, different positions of the motor will give different readings. The results I got here is the lowest value in ohm when stand still, lowest of at least five different, random positions.

The lowest result using my milli-ohm meter with Wheatstone bridge, including about one feet long wire.
Yellow - Black ~0.9 ohm
Yellow - Blue ~0.62 ohm
Yellow - Green ~0.64 ohm
Black - Blue ~ 0.65 ohm
Black - Green ~ 0.73 ohm
Blue - Green ~ 0.86 ohm

[edit 2]
New measurement of generated voltage, now with this setup with two separate multimeters:
Yellow - Blue : ~0.58V
Yellow - Green : ~0.56V
That is pretty much identical given all the error factors.

My guess so far
As earlier suggested, this may indicate that I can choose to connect e.g. Yellow-Blue to get the fan into half speed, and then make a boost by connecting Black-Green (same order to avoid short). Or possible even more stages if all the wires but one is connected, to achieve a way of regulate the speed in 3 steps.

When remembering the car was actually running, I'd remember this fan had a tendency of short boost just after breaking down to a halt.

Why the car manufacturer choose to make a complicated fan instead of a more simple approach using fixed PWM steps - I guess this approach may have a lower tendency to not cause the fan to completely die in case of failure, it is after all the cooling of the engine.

 

[vtech]

Hi.

Same car as discussed here:

Wire designation on complex coloring schemes (Nissan 2000)

Hi. I'm helping a friend that have a Nissan x-trail from 2001 with an electrical issue. We suspect there may be some fault to the actual wiring itself (car have be subjected to rough treatment some years back). In order to help myself to locate the fault, I make a schematic (my own, that only...

www.electro-tech-online.com

So, we took out the radiator fan because we initially taught it was dead. However, I managed to get it to run by using a small simple 12V transformer+rectifier (doesn't immediately broke if shorted, and too little maximum current to kill the fan motor).

But the question is why car manufacturer seems to put four wires to a fan? The measured resistance between each wire is too low to determine anything, therefore I tested on bench.
The test results yields the following observed result (omitting all test resulting in running in opposite direction).

See table below (I'm somehow not able to put cursor after table, so the table have to come last)

I also measured the voltage between the poles not used when fan was fed by two wires, i.e. while fan running for second last line in table, I measured just above 2.5VDC between black and blue (the weak transformer only manage to output ~6V to the fan running).

Because I doesn't have tested with a proper PSU yet, I'm not sure if the fan is fed using all four wires (like in last row) using a proper 12V supply will simply cause the fan to run faster (because the weak transformer itself is the main limiting factor). But then again why waste an extra wire if it turn out 3 wires should be enough ?

black wire	Yellow wire	Green wire	Blu wire	Result (does it run)
negative	nc	nc	plus	runs ok
negative	nc	plus	nc	runs ok
negative	plus	nc	nc	No running. Near short (around 2 ohms)
nc	negative	nc	plus	runs ok
nc	negative	plus	nc	runs ok
negative	negative	plus	plus	runs ok

I can understand trying to help a friend but you are going about it incorrectly;
Unless you have the specific vehicle documentation and/or know-how, you are more likely wasting your time;

The "cooling Fan not working" is not as simple as a computer fan, there are many factors involved. Among other parts of the vehicle, EVERYTHING is controlled by the main computer thru "CAN" bus, there are Fan relays that control the speed from low to high to off --strictly dependent to the condition of the engine's coolant temperature.
On top of that, there is OBD system that will pop up error codes when there is specific faults and you need a scanner to read that---are there any "check engine" lights on the dashboard?

Suggest doing some research before getting too involved...

 

[Grossel]

I can understand trying to help a friend but you are going about it incorrectly

yyyes, but we have a "pizza/beer/beef deal" so to speak so I don't mind digging down this rabbit hole as long there is some free dinner in sight

 

[Diver300]

Yellow - Blue : ~0.58V
Yellow - Green : ~0.56V

Green - Black : 475mV
Yellow - Blue : 461mV

That would make Yellow - Black (via green) around about 1 V.

I think that Yellow - Black may be slow speed and most of the others, for instance Yellow - Blue, high speed. If you have a power supply that cannot produce much current, Yellow-Black may run faster than Yellow - Blue. In the car, where lots of current is available, the fastest speed will be achieved by supplying the brushes that have the lowest generated voltage when you spin the motor by hand.

PWM would tend to be electrically noisy with something as big as a fan.

 

[schmitt trigger]

If you don’t have the PSU with the correct voltage/current…. In the past when facing the same problem, I removed the battery from one of my vehicles for testing.

I know some may jump on me for suggesting this approach, but I trust that you are knowledgeable enough to mitigate any risks.(*)

(*) Back when I was in college, I had one old fashioned electromechanical police siren, the one with a large motor which spun a large rotor.
When we went to games to cheer our school team, we removed the battery from our vehicle to power the siren. The worst that happened is that we depleted the battery in a particularly contested game.

 

[Grossel]

Sure, I'd not risk a battery short, but I have actually laying a proper motor disconnector/fuse in store so to prevent it to burn.

 

[Grossel]

Yellow-Black may run faster than Yellow - Blue

Yellow-Black create a near-short without the motor spinning. Likewise for Blue-Green. Also, the measured voltage generated between those wires are fluctuating around 0V (never measure DC over 10mV) for the possible speed range I can produce by hands.