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Thread: Infinity Box and A/C wiring of Trinary Switch

  1. #1
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    Infinity Box and A/C wiring of Trinary Switch

    I am building the 33 Hot Rod and having a difficult time with wiring the trinity switch to work properly.

    My build is a simple 302 carbed setup no fancy black boxes or electronics.

    I am not a complete idiot on electrical systems as I have a working background in high voltage systems and electronic switch gear.

    This trinary switch hookup is kicking my butt.

  2. #2
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    It's really not difficult. This video may help.

    https://www.youtube.com/watch?v=l604JCZx_ow

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    I have Infinity Wiring but I don't think it makes any difference. The trinary switch is two poles, one pole operates the fan the other the AC compressor clutch. The fan side closes when the refrigerant reaches about 150 psi on the high side. The clutch side is closed when the refrigerant pressure is between 30 and 300 psi. This keeps the compressor from operating when the charge is low or the pressure is above a normal max. Here is my schematic for the trinary.

    trinary.jpg

    Due to the high current a fan draws they are most always controlled with a relay. There are two ways to operate the fan with the relay. One is applying +12V to the relay coil and controlling the ground path. When the coil is grounded the relay is energized and the fan runs. The other method is providing a constant ground for the relay coil and controlling the source of the +12V for the fan relay coil when it is to be energize. My fan relay is controlled through grounding so +12V is run from the fan relay voltage source to the relay and the ground wire goes to the trinary and other control points such as the ECU and dash switch. I have the Coyote PCM/ECU and it grounds the fan relay to make it energize based on engine temperature hence the reference to the ECU on my schematic.
    King
    Roadster #8127, ordered 7/12/13, received 9/11/13
    http://thefactoryfiveforum.com/showt...4-Coyote-Build

  4. #4
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    Sending a ground signal to the same pin on the ECU that feeds to the fan control relay may result in a fault code. The ECU normally sends a ground signal to the fan relay, based on a variable voltage signal from the coolant temp sensor. The trinary switch may send a ground signal to the fan relay when the engine temp is low. The computer then faults, because of the ground signal sent before the engine is hot enough to require the fan.

    I kept my ECU control of the fan connected as it came from the factory. The trinary switch control of the fan is done with a separate relay that feeds a second source of power to the fan. That way the ECU does not see the ground signal from the trinary switch. The two relays operate independently.
    Last edited by DaveS53; 09-07-2017 at 12:19 PM.

  5. #5
    2bking's Avatar
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    Quote Originally Posted by DaveS53 View Post
    Sending a ground signal to the same pin on the ECU that feeds to the fan control relay may result in a fault code. The ECU normally sends a ground signal to the fan relay, based on a variable voltage signal from the coolant temp sensor. The trinary switch may send a ground signal to the fan relay when the engine temp is low. The computer then faults, because of the ground signal sent before the engine is hot enough to require the fan.
    Unless you know for sure this will happen, it does no good to suggest that it will happen. In fact, it will not happen. The harness has a AC blunt lead input to the PCM and PDB so the PCM knows when the AC is on. The 2013 harness included a PDB that had a relay added to ground this signal line when the AC was on creating a condition where the fan ran continually. The trinary does exactly the same as that relay. I removed the relay so the fan could also be controlled by the trinary. My understanding from the experimenting I did was that putting +12V on the AC blunt lead changed the engine idle RPM. It may also prohibit the fault code you allude to but I don't know that. I do know I have over 4k miles now and the fault code has never showed up.

    The 2015 controls pack may work the same way but I don't that. I only have experience with the 2013 pack.
    King
    Roadster #8127, ordered 7/12/13, received 9/11/13
    http://thefactoryfiveforum.com/showt...4-Coyote-Build

  6. #6
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    The fault will happen if you're using a GM crate engine, with their ECM. It only controls the engine and nothing else.

    You may be entirely correct that Ford added a specific lead for this issue with the Coyote. That would be different than sending the trinary switch ground signal to the SAME ECU pin that sends a ground signal to the relay that controls the fan in response to the engine temp.

    Neither applies to the OP's situation. He has the simple setup shown in the video.

    Here's a link to a wiring diagram that should be applicable. The 30 or 40 amp power supply will probably be available from the infinity box.

    http://www.vintageair.com/DownloadsS...%20Diagram.pdf
    Last edited by DaveS53; 09-07-2017 at 03:36 PM.

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