CX air-con wiring diagram
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  1. #1
    skp
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    Default CX air-con wiring diagram

    I've got a few issues with a CX cooling fans...
    This is a 1980 (-ish) model, 2400, C-matic with air-con.
    The wiring diagrams that I can lay hands on don't conform to the Aussie cars.......

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    The fans are sequential, working in series then parallel as the temperature rises, and the air-con is switched on.
    All the diagrams i have only show the fans operating 'independently' - no half speed stage where they operate in series.

    Can anyone provide me with a correct layout?
    I know I had this sorted out on another car some years ago, but I can find no trace of my notes - damn!

    skp

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    It's an aftermarket/dealer fitted system on some... So that maybe where the confusion is coming from. I'm guessing it'll all burst back to life if you pull all the relays and clean the connections. Some have a twin thermister switch on the radiator. Some have a single on the radiator and the airflow sensor out in the middle of the radiator.

    The CX wiring schema isn't easy to understand. Here's how it will work ( I chucked a set of EL fowlcan fans on my crappy old land rover and this is how I wired them ).



    So using 3 relays and a twin thermister switch, you can run the fans in series or parallel ( I even used the CX temperature switch in the land rover ... it screwed straight in). You should find an extra relay there that will also earth the low switch when the A/C is switched on. If you want to go one better .... Fit a switch to your receiver drier that also trips at higher pressures, and wire this to the high fan switch.... so if the A/C is working hard, you will switch the fans onto high speed.

    OH yeah ... the failure mode with most wiring issues (or a stuffed fan motor ) is almost always no low speed fan (as it's a series circuit) and only one fan on high speed. If this is the case, you will also have no A/C fans as they drive the ( broken ) series fan circuit.

    seeya,
    Shane L.
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  3. #3
    1000+ Posts robmac's Avatar
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    Shane,

    I respectfully suggest the fuses for the motors are better placed in the feed to the relays, rather than the load circuit to the motors.

    In the former position the relays are fused in the event of failure (short cct).

  4. #4
    1000+ Posts Ken W's Avatar
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    If you have a haynes CX manual, look at the circuit diagram for the Prestige May 1978 to July 1979 Fig 13.53 on Pg 254 in my manual. The LHS side has the series parallel fan circuit with the radiator fans as items 3 and 4 being controlled by four relays. Engaging aircon closes relay 19. When relay 19 or the low temp/air temp sensor 14 (which is in parallel) closes, relay 18 is closed and power is applied to the two fans in series - low speed. When the high temp sensor 15 closes, then both relays 45 and 46 triggered placing the fans in parallel - high speed. The only downside of this circuit is that if the low temp sensor has not triggered before the high speed sensor (this could happen if car is sitting still and there is no airflow through the radiator to heat the low temp airflow sensor), then only one fan will run at high speed.

    Cheers, Ken

  5. #5
    skp
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    My Haynes are clearly different editions... neither corresponds to you numbers..
    None-the-less, your explanation is clear. This still doesn't correspond to what I recall of the setup for this model. As I recall, one ( or perhaps two ) fans were activated by the air temp sensor, at slow speed. With increasing temperature, one fan went to high speed, then both. Activating the air-con brought in one of the fans at high speed, no matter what.
    Maybe I mis-recall this.... But I'm pretty sure that is how my old CX ( identical to the one I am dealing with now) was set up.
    This seems to be close to the setup for the post '83 CX25 models...

    skp

  6. #6
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by robmac View Post
    Shane,

    I respectfully suggest the fuses for the motors are better placed in the feed to the relays, rather than the load circuit to the motors.

    In the former position the relays are fused in the event of failure (short cct).
    Oh, that's not my diagram ... I just added one fuse in the power feed wire to the relays. I "borrowed" the circuit diagram onliine as it's a pretty good overview of how parallel/series circuits work.
    'Cit' homepage:
    Citroen Workshop
    Proper cars--
    '85 Series II CX2500 GTi Turbo I
    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual

  7. #7
    1000+ Posts Greg C's Avatar
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    They were all Grande Exportation models and all had the series parallel circuit similar to what DC posted. The original wiring has one crossover relay and to switch relays. A very elegant circuit. First is to check all connections, especially the ones that feed the fans, clean with electronic contact cleaner and make sure they are tight before you start replacing relays.
    Mine

    CX Prestige
    Toyota Prius

    In the family

    Xantia SX

  8. #8
    skp
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    Sounds right, to my memory.
    Thanks all.

    skp

  9. #9
    1000+ Posts Ken W's Avatar
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    skp,

    Here is the page from my Haynes CX Manual era 1990s.

    Let me know if you want more details or scans.

    Cheers, Ken

    CX air-con wiring diagram-cx-fans003-af.jpg

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