I am working on wiring the ventilated portion (a fan) of an automotive seat. The fan has 3 wires coming from it, then it also has an additional ground wire. The ground wire does not go to the connector plug, but rather is attached to the metal base of the fan.

The connector for the fan has 3 wires. Per the wiring diagram:

Black - Ground
Red - Power
White - PWM Control
Blue - additional ground

In the vehicle where the seats were originally installed there is obviously a fancy computer system that controls the speed of the fan. I would be happy to simply run the fan at full speed.

What I have discovered, through some trial and error (and some dumb luck). If I connect the Black to ground, Blue to ground, and Red to 12v the fan does nothing. However, if I also apply ground to the white wire in an off/on/off/on sequence after a few times the fan kicks on. It seems I need to continue with that sequence or the fan shuts off.

Is there an easy way to get it run at full speed? If not is there a PWM that i can add to the wiring that will create an ON/OFF to ground for the white wire?

The fan is made by Gentherm, but I can't find any detailed info about it.

TIA

 

Did you try connecting the white to 12V? That would simulate 100% duty cycle PWM. I would use a 1K resistor in series to avoid possibly damaging it.

 

Did you try connecting the white to 12V? That would simulate 100% duty cycle PWM. I would use a 1K resistor in series to avoid possibly damaging it.

I did apply 12v to the white wire (with black to ground and red to +12v) and the fan doesn't move. (did not use a resistor).

 

Here is a video of me trying to get the fan to run. Video Maybe this is helpful.

 

So build a simple PWM controller. A 555 and some passive components should do just fine.

Here you can get six PWM Controllers for $12.
https://www.amazon.com/Motor-Controller-Control-Switch-Dimmer/dp/B08T5TJWYH/ref=sr_1_16

 

Wait a minute. That fan of yours doesn't run without a PWM Pulse. That controller probably won't work for your need.

 

Wait a minute. That fan of yours doesn't run without a PWM Pulse. That controller probably won't work for your need.

Correct, when I apply 12v to the red wire and ground to the black with nothing attached to the PWM (white) wire it will not run. I have applied 12v to the PWM wire and it wont run. Someone suggested trying 5v on the PWM wire to see if it will work. I am skeptical that will work.

The only way I got the fan to run was by rapidly scraping the PWM wire to ground. I believe I created a PWM of sorts where I was basically sending the fan (through the PWM wire) an ON/OFF/ON/OFF signal. So, I currently believe that I need some device that can provide an ON/OFF/ON/OFF signal where it turns the ground on and off to the PWM wire.

Simply attaching the PWM wire to ground does nothing. It seems to want that on off signal? Or maybe I am sending it a certain resistance as I rapidly move that wire on a ground surface.

 

Looking through my limited collection of 555 circuits for a variable duty cycle circuit. When I find one I'll post it.

Better still, ask @Wendy. She has MANY circuits you can look at and copy. I'm confident she will help you.

 

Found this in Wendy's collection:
https://forum.allaboutcircuits.com/threads/submission-555-pwm-oscillator.24028/
I've cut part of the circuit out. The output at pin 3 should probably be connected to your white wire.

To be sure - this is Wendy's drawing, not mine.

 

Since your motor has a PWM input there should be no need for the rest of the circuit. I trust you're looking at Wendy's post on the subject. There's lots to learn.

 

So, I currently believe that I need some device that can provide an ON/OFF/ON/OFF signal where it turns the ground on and off to the PWM wire.

Which is what a PWM signal does. Your device apparently has a pullup, so it sees high when mot connected and low when connected to ground.

The only thing that remains is to determine what voltage the PWM should be.

See if you can get a voltage on the PWM input when powered on.

 

Which is what a PWM signal does. Your device apparently has a pullup, so it sees high when mot connected and low when connected to ground.

The only thing that remains is to determine what voltage the PWM should be.

See if you can get a voltage on the PWM input when powered on.

My apologies, I am a bit confused, or maybe I have not explained this well.

You mention needing to determine voltage of the PWM. But it seems when I apply + to the PWM nothing happens with the motor. Only when I rapidly move a wire to ground then off ground (connected to the PWM wire) does the motor start to work.

It seems applying +voltage to the PWM wire does nothing.

 

You should never apply 12 volts to a fan's PWM signal wire without knowing if the fan can handle it...that voltage can damage most PWM fans.

Contact Gentherm give them the model number and ask what PWM signal the fan requires, then come back and someone here will instruct you on how to create it.

 

It seems applying +voltage to the PWM wire does nothing.

Apparently it needs to pull the PWM line to ground to work but not at a 100% duty cycle.
Here's my version of a 555 circuit with an appx 90% fixed duty cycle using pin7 to drive the PWM input.

 

You should never apply 12 volts to a fan's PWM signal wire without knowing if the fan can handle it...that voltage can damage most PWM fans.

Contact Gentherm give them the model number and ask what PWM signal the fan requires, then come back and someone here will instruct you on how to create it.

Gentherm wont provide that information. They make this fan for Chrysler who then uses it in an OEM application. They consider it proprietary information. They make it to Chrysler specs and advised me to talk to to Chrysler. You can imagine what calling Chrysler for such information would yield.

 

Gentherm wont provide that information. They make this fan for Chrysler who then uses it in an OEM application. They consider it proprietary information. They make it to Chrysler specs and advised me to talk to to Chrysler. You can imagine what calling Chrysler for such information would yield.

Then I would try jigging up something using a low side switch only before I tried applying any positive voltage.

After that I would start with 5 volts then 12.

 

Then I would try jigging up something using a low side switch only before I tried applying any positive voltage.

After that I would start with 5 volts.

I have already applied 12v to the PWM (white) wire. Obviously, I have no idea if that messed up anything internally on the fan. I can pull the fan from the passenger seat to do further testing.


When you say a low side switch you mean using a PWM that will turn the negative on/off?

 

My circuit shown in post #14 is a low side switch using the open collector transistor output on pin7.
The values of R1 and R2 may need to be adjusted but think the values listed are a good starting point.

 

Apparently it needs to pull the PWM line to ground to work but not at a 100% duty cycle.
Here's my version of a 555 circuit with an appx 90% fixed duty cycle using pin7 to drive the PWM input.
View attachment 294963

Is it odd that it would not work to ground (ie 100% duty cycle)?

 

Might be a safety issue and I suspect the blue wire is a sensor out to the control circuit called Tach.