S70 1998 with 166k mi A/C stopped working

Discussion in 'Volvo S70' started by mark barron, Jul 18, 2008.

  1. mark barron

    mark barron Guest

    Second attempt to join group.
    The A/C was working fine. Then I replaced the alternator and
    installed a new cabin filter.
    When the A/C stopped, I assumed I had pinched a wire installing
    the ALT. Visual inspection dismissed the possibility. Neither
    the A/C nor the Recirc Light light or flash. There are two
    wires feeding into the inboard side of the compressor. With
    all the requirements met (fan on, A/C button in, hot cabin,
    knob set to maximum cooling) there is zero voltage input to
    both of these wire to the compressor. Jumping the two pressure
    switches on the refridgerant lines had no effect. Nothing
    seem to make the clutch engage. This appears link a blown
    fuse or fusible link, Please advise.
    Do I need a Control Panel? Can a control panel be
    mark barron, Jul 18, 2008
  2. mark barron

    Tim.. Guest

    Can you confirm that with the AC button pressed that the green light does
    NOT come on?

    If that is the case, then you have lost power to the switch for some reason-
    initially check the multiplug at the rear of the HVAC controls. (I assume
    you have manual AC , rather than climate??)

    I can check and tell you which fuse the a/c is supplied from if you like.

    The ECU has ultimate control of the compressor clutch and condensor fan, but
    the green light should still come on.

    Tim.., Jul 19, 2008
  3. mark barron

    mark barron Guest

    Thanks for your reply. The Green Light does not come on ever(since AC
    stopped) I have disconnected and reconnected the two multiplugs at
    back of Control Panel. I do NOT have automatic climate control,
    but have single switches for both A/C and Recirculation. Temp control
    knobs are surrounded by red and blue "arrows". Fan is manually
    controlled. I have checked the two fuses that seemed related,
    - Climate diagnostics
    - Fuse 31
    I wish I had a pinout for the two multicables on the Multicable.
    I think the CP must have gone bad. I hate to buy one before
    I can check the expected voltage at the CP. I find plenty
    of used CPs with automatic climate control, but none without
    on Ebay.
    Do I understand it correctly? If the fuse for the CP is good,
    the light will come on. Is there anything else that could stop
    power getting to the green light? I need a pinout to check for a ground
    connection. Perhaps I can assume that a brown cable is ground.
    I am finding no OBD II error codes.
    There are two pressure sensors on the refridgerant lines that stop
    the clutch engaging --- any other things that do this outside the ECU?
    mark barron, Jul 19, 2008
  4. mark barron

    mark barron Guest

    Thanks so much for your reply.
    The green light on the A/C switch does not come on
    when pushed in,ever . I have checked fuses, including #31 Climate
    and one labelled "Climate diagnostics" #5? I have removed
    and reseated the two multicables at the back of the Control
    Panel. A/C is not automatic. There is a single button each
    for the A/C and Recirc and the Temp Control buttons are surrounded
    by red and blue "arrows". The Fan is manually set. I am
    seeing plenty of CPs with automatic climate control
    at Ebay, but none without. I think I need a pinout for the
    two multicables to see what is arriving and what is leaving.
    I hate to buy a CP without knowing for sure it is bad.
    I can not do that without a pinout, as I see it. I have
    a Haynes Manual , but it does not have an AC wiring map.

    At the back of the Control Panel there are two multicable
    connectors. My finding with car idling
    Connector #1 Gray Body with six wires
    Reading directly from connector wires,disconnected from CP
    Blue/Orange 0
    Blue/White 0
    Blue 0

    Grey/Green 0
    Blue/Brown 0
    Yellow/Purple 13.7

    Connector #2 Green Body with 22 positions but 15 wires
    There is a 12 position and a 10 position side
    My finding with car key in position 2, not running.
    Reading directly from connector wires,disconnected from CP
    10 position side
    1 - Gray 0.06
    2 - Gray/orang 0.06
    3 - Grey/Red 0.06
    4 - Grey/Black 0.06
    5 - Grey/White 0.06
    middle break here
    6 - Yellow/Purp 12.71
    7 - 10 empty

    12 position side
    1 - Gray/Brown 0.04
    2 - Brown/Orange 0.04
    3 - Brown/Pink 0.03
    4 - Brown/Green 0.03
    5 - Brown/White 0.04
    6 - Black (Grnd) 0.0
    middle break here
    7 - Red 12.4
    8 - Pink 0.03
    9 - empty
    10 - empty
    11 - empty
    12 - Gray/Blue 0.006
    mark barron, Jul 19, 2008
  5. mark barron

    mark barron Guest

    mark barron, Jul 20, 2008
  6. mark barron

    Tim.. Guest

    Without looking at the wiring diags (its 3am!) i am fairly sure that the AC
    switch takes power from the Fan switch- i.e. if the fan switch is in
    position 1 or greater, then the ac switch gets power. I can let you know
    which wire should have the ac signal on it when the switch is pressed. This
    goes straight to the ecu. You may be lacking an earth at the CP which is
    preventing the green light coming on, but this will not affect the ecu
    engaging the compressor.
    This is not as simple as it first appears.

    There is a low pressure switch (on the central bulkhead- 2 wire) which will
    open when the low side has insufficient pressure caused by a low charge- its
    there to protect the compressor.

    The second 3 wire sensor by the slam panel is a variable pressure transducer
    which the ecu monitors to control the condensor fan, and compressor clutch
    to balance what the evap temp sensor tells it.

    There is also a super heat switch on the back of the compressor.

    Hope this helps so far.

    Tim.., Jul 20, 2008
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