This IAC stepper controller is designed to control a typical 4 wire IAC Stepper Motor from a ground switching PWM signal from your ECU.


It has been tested with GM , Marelli and Renault type 4 wire stepper motors but should work with virtually any standard automotive 4 wire idle stepper motor.

 

Contents

1 x PWM2Stepper Control Module
1 x Molex IP67 Connector
7 x Molex connector terminals
1 x Tie strap mounting base


Operation

This module converts the ECU PWM 0% to 100% signal into steps for the IAC
It will control the stepper from fully closed at 0 steps to open at 200 steps.
Whilst many steppers will go to around 240 steps maximum at around 200 steps they are effectively fully open in terms of air flow.
We choose this 0 to 200 range of operation to keep the calculations easy.

Typically 1% PWM change equates to 2 steps change so,
10% PWM = around 20 steps
50% PWM = around 100 steps
100% PWM = around 200 steps

Unlike other converters this module is not “ Always ON “ so does not overheat the module or the stepper motor when the stepper is stationary.
After a few seconds of no movement commands it goes into a sleep mode shutting off the stepper power and then reawakens when it next receives a move command.

 

Physical and Technical Specifications

Waterproof assembly designed for engine compartment mounting.
Complete with IP67 waterproof Molex connector for plug in connection
Dimensions = Approx 50mm x 50mm x 30mm

  

Operating Temperature

Ambient temperature of engine bay should not be more than 60 degrees C
( Protect from higher temperatures using shielding or relocation of module )

 

Operating Voltage

Minimum normal working voltage = 9 volts
Maximum normal working voltage = 15 volts
Short term Spike voltage = 20 volts

If the voltage drops below 9 volts the stepper motor may become lost and not open fully.
If this happens, for example during cranking with a very discharged battery, it will reset itself during the next ignition key cycle from OFF to ON

 

PWM Signal Type and Frequency

The PWM signal input to this module is the  “ Ground Switching “ type. ( most common ECU output mode ) This means at 0% PWM operation the PWM signal held is High ( 12 volt ) by the ECU and at 100% the PWM signal input is held Low ( 0 volt ) by the ECU
 
The unit is designed to work with an input between 90Hz and 300Hz with the optimum being the commonly used 100Hz output frequency.
Where possible for optimum results set your ECU output to 100 Hz output frequency.

 

Electrical Connections

Connector Pin 1 = Coil 1 Positive
Connector Pin 2 = Coil 1 Negative
Connector Pin 3 = Coil 2 Positive
Connector Pin 4 = Coil 2 Negative
Connector Pin 5 = PWM Input

Connector Pin 7 = 12 volt Power  ( from ignition key or ECU controlled power )
Connector Pin 12 = 0 volt Ground

 

Do I have Stepper Motor Type A or Type B ?

Using a multi meter test for continuity on the two centre stepper motor pins.
= If you results show no continuity then it is probably Type A
= If you show resistance reading of typically 40 to 60 ohms then it is probably Type B
 

Type A motors
Commonly used by GM and after market throttle bodies such as Holley and Edlebrock etc.
Also used in our Webcon Retroject throttle body
 

Type B motors
Commonly used by Magnetti Marelli, Renault and  Citroen
Also used in our combined standalone Idle Stepper motor and housing assembly.