Yesterday my blower motor suddenly stopped working when I started the car in the morning and my climate control display started flashing (indicating a fault). I immediately suspected a faulty blower motor as it started making chirping and screeching noises intermittently since February this year.

The issue is, I'm not exactly sure if the fan control module is faulty as well or just the blower motor, I did a voltage test with digital volt meter at the two wires going into the blower motor coming from the module and got 12,4 volts at the power when ignition is on and 12,4 volts at the ground when the fan is turned on (but no ground when fan is off).

The problem is I can't tell by reading the repair manual if the voltage should be 12 V even at different speeds, it seems to me that all the module does is it acts like a variable resistor to control voltage output for the fan speed as well as a relay. When the ignition is on it sends power to the fan but there's no ground, then when you turn on the climate control it closes the ground to the fan so it starts to spin but it should show different voltages depending on the desired speed, when I see a constant voltage at ground and power regardless of input it makes me think that the resistor part of it is faulty since it can't limit the voltage (would make blower motor work at full speed).

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(current flow diagram)

Reading the diagram J126 (fresh air control module) has five wires connected to it (6-slotted terminal), three from the climate control unit (E87/J255) which sends input from the driver and other stuff and then two wires going to ground (53 which leads to ground point 99 in another page) and power (Fuse 36). There's two wires directly going to the fan motor (power/ground) as well shown in the diagram without much detail.

Is the control module supposed to send constant voltage at different speeds to the blower motor or am I misunderstanding how a blower motor control module works? It seems unlikely that both the control module as well as the fan stopped working at the same time.

For reference:

Car: 2004 Seat ibiza 6L

Mileage: 110000 km (63000 miles)

1 Answer 1


The blower control module may be using pulse width modulated (PWM) control to the blower - high speed digital switching of 12v power that may not be seen on any multimeter but seen as s 12 volts. PWM switches 12v on/off at high speed to vary the current that controls blower motor speed. An oscilloscope can display high speed signal switching as one way to view pwm signals, seen as a waveform. The simplest way of isolating electronics from blower problems is powering the blower directly from the battery. If the blower does not come up to speed immediately or acts erratically, then it's likely a worn out motor. If you have another 12 volt motor, even a 12v lamp, you can wire it to the connections and see if either motor speed varies or lamp brightness changes. This would verify the control board is operating as designed.

  • I ended up taking apart the dash and removing the blower motor only to find that it actually works but very erratically, it makes a screechy noise occasionally and there's alot of friction when it spins leading me to believe that it's the motor at fault. I suspect the culprit is either worn out bushes leading to bad contact or simply dry bearings/bushings putting too much strain on the motor when it spins.
    – Aden
    Aug 16, 2023 at 22:47

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