The 3-wire IAC valve - Operation - Testing - Maintenance

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Here I am talking about the IAC of 3 cables. How to perform tests, with tester, multimeter measurement and electrical diagram that will let them know if it works or not.

3-wire IAC valves.

How does it work?

Three-wire IACs use AISSIN or compatible systems and work somewhat like their two-wire sisters, by pulse-width modulation. This means that longer ignition pulses open the mechanism and short ignition pulses close the mechanism.

In the case of the 3-wire IAC, there is then a common cable for two coils. One opens all and the other coil closes the entire IAC. When the power is off, the IAC is in the central position allowing some air to pass to the intake manifold. This is done by an internal spring that has the valve.

If the computer wants to open the valve, it gives long pulses to the opening coil and less to the closing coil. To close it does the opposite. In the following figure you can see this behavior in the pulse train.

Pusos PWM IAC 3 cables


It is much more accurate than the Motorcraft IAC that only has two cables. This is because over time the coefficient k of the spring on which this IAC depends is lost, and with this the train of pulses must constantly vary to achieve the target RPM, which translates into an idle or irregular minimum of the Engine RPM

On the other hand, for this IAC of 3 cables, the spring only works when it is damaged, taking it to a safe point of operation for the motor (which does not turn off).

 

How to identify the cables of the IAC of 3 cables?

The pins of this connector are 3:

Terminal

Functioning

RSC

Señal modulada para cerrar la IAC (señal negativa)

+B

Tensión de mando (señal +12V)

RSO

Señal modulada para Abrir la IAC (señal negativa)

 En la figura siguiente se puede ver una típica IAC de tres cables.

conector iac 3 cables

With a multimeter it is very easy to identify which of the pins is the common one. (Usually the middle one.) This is done with the ohmmeter and the resistance between terminals is measured. Following this procedure:

Carry out the measurements as indicated in the image below:

medición iac 3 cables

The measurements should give as what they show in steps 1, 2 and 3. These correspond to the diagram seen to the right of the image, where the central would be the common and the lateral terminals are those of the coils.

In this case, the terminals would be as seen in the following table:

Terminal 1

Terminal 2

Terminal 3

RSC

+B

RSO

 

Apart from the previous measurements, you can also give us something like this:

medición iac 3 cables

Note that a small change in the diagram, modify the measurements and with this we must intuit our connector that would be as shown in the following table:

Terminal 1

Terminal 2

Terminal 3

+B

RSO

RSC

 

As you can see, we should always analyze the measurements we have. It should be noted that strange values to the following, we can assume that the IAC is damaged.

Resistors of the IAC 3 cables

1 - Winding between 17-25 ohms when it is cold.

2 - Winding between 22-28 ohms when hot.


How to test the IAC 3 cables?

It's very simple and you do not need a tester for this. already having the terminals identified, we can directly energize the IAC following the following diagrams:

hacer funcionar iac 3 cables con probador

We connect the positive 12V battery to the terminal + B which in this case is the central terminal, and then if we want to close the valve, we only have to connect the negative to the RSC terminal, and if we want to open it, we connect the negative to the RSO terminal. And ready, as simple as that. Hehehehe

Cleaning the IAC 3 cables

Cleaning it consists of pouring solvent into the mechanism of action of the IAC to remove the black soot from the combustion residues. Try as much as possible to place the valve so that the dirty liquid comes out of it so as not to clog the piston or the shaft.

After cleaning everything you can with solvent, if they operate it in the way you teach them, they will make cleaning it much more effective. Since the movement while pouring the solvent removes the soot that is trapped where we can not physically reach with a rag.

I hope you enjoyed this short tutorial, if you have any questions or suggestions, below in the question box you can do them.

Questions or suggestions

In the box below questions.

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Made by:

08/08/2018

Mechanical Girl

Dennis García.

Terminal

Functioning

RSC

Señal modulada para cerrar la IAC (señal negativa)

+B

Tensión de mando (señal +12V)

RSO

Señal modulada para Abrir la IAC (señal negativa)

Grade 
08/09/2018

Excelente

Gran post

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The 3-wire IAC valve - Operation - Testing - Maintenance

The 3-wire IAC valve - Operation - Testing - Maintenance

Here I am talking about the IAC of 3 cables. How to perform tests, with tester, multimeter measurement and electrical diagram that will let them know if it works or not.

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2 Question(s) answered

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  • Asked by ANDREA CHACIN
    on 08/09/2018
    Hola, gracias por compartir, este es un excelente articulo y muy util gracias!!! Answer:
    A ti Andrea por la visita.
  • Asked by miguel antonio
    on 08/13/2018
    los 2 cables que van alos estremos del conector del iac como logro medirlos .grasias Answer:
    Bueno Miguel en el artículo aparece el diagrama. En teoría para una IAC Toyota tiene que darte el doble de resistencia, unos 40 ohms con un ohmimetro.

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