Omega Electronic Climate Control Problem

Discussion in 'Omega' started by markrl, Nov 15, 2005.

  1. markrl

    markrl Guest

    Hi, I have a 1998 3 litre Omega Elite fitted with the digital climate
    control which has started to develop a very annoying problem now that winter
    has arrived. On a cold day with the temperature set and the system heater on
    no problem on a short journey. However on a longer journey with the cabin
    pleasantly warm it suddenly seems to go into rapid cool down mode suddenly
    blowing out cold air and if left on automatic the fan speed increases as if
    on hot summer day mode. The only way then to get any warm air is to turn the
    temperature right to the top on to the "Hi" setting which overrides the
    auto settings and of course then becomes very hot. If the vehicle is stopped
    for a while the system seems to start working again OK. This problem only
    occurs on longer journeys when the heater has been running for some time and
    I would suspect this may be a problem with whatever sensor controls the
    interior cabin temperature. Its as if its suddenly erroneously telling the
    air conditioning system its very hot, which of course then responds by
    turning on the air conditioning, not very desirable when its only 3 degrees
    I should be grateful for any advice from anyone with a bit of specialist
    knowledge I fear this may be an expensive trip to the main dealer.

    Many thanks - Mark
    markrl, Nov 15, 2005
  2. markrl

    me140 Guest

    The sensor is behind the slotted hole on the climate control panel - they do
    get full of dust so give it a blow out - not convinced this is the problem
    though but worth trying.
    me140, Nov 15, 2005
  3. markrl

    mikeFNB Guest

    my first thoughts also.

    clean the sensor

    then its time for a paperclip!

    mikeFNB, Nov 16, 2005
  4. markrl

    666 Guest

    First please reset ECC by pressing 'Auto' and 'Off' simultaneously for around 5 seconds.
    AC compressor is not expected to work below some outside temperature, around +4 Centigrades if I remember.
    666, Nov 18, 2005
  5. markrl

    Markrl Guest

    Many thanks for all your suggestions. I have cleaned the sensor apature with
    a vacum cleaner and done an "Auto and Off" reset. The system is presently
    working but I suppose the next long journey will tell (normally about 1
    hours driving produces the problem). Not entirely sure what you mean by its
    time for a paper clip (poked in to unblock the apature intake ?). The other
    thing I was wondering is there an air intake sampling fan to draw air in
    from the cabin and could this have failed ?

    Many thanks again
    Markrl, Nov 20, 2005
  6. markrl

    Mike Dodd Guest

    Paperclip refers to a diagnostic technique of shorting two pins on the
    diagnostic connector to obtain a fault code. I've heard that this can be
    done with the various computers (including climate control) but have
    only actually experienced this with the engine / exhaust management
    system. "Paperclip" is the cheap way to short the two pins, personally,
    I could never be bothered to buy a paperclip, and always used a piece of

    Back to your problem.

    I'm sure that cleaning / etc. is the best place to start. However, from
    your clear description of the problem where you suggest an intermittent
    fault that results in the a/c failing to recognise the cabin
    temperature, this suggests a failure of the signalling between the a/c
    management and the sensor. Probable causes off top of my head (in order
    of likelyhood) -

    1) Dodgy connectors (try unplugging / cleaning / reseating any you can
    find between a/c controller and the sensor)
    2) Dry-joint or failed solder pad - either at the sensor (if mounted to
    a PCB) - requires re-flowing or similar - hard to diagnose until you
    find the problem
    3) Failed sensor (internal fault) - should be noticable by manipulating
    the sensor with the a/c running. If found, then replace with like from
    4) Failed loom - real bugger to diagnose, easiest way to take the loom
    out of the equation is to bi-wire the sensor to the controller -
    duplicate the wire run for each sensor wire (e.g. if the sensor has two
    wires in the cable loom going to it then run two parallel wires back to
    the controller). This only needs to be a temporary hook up to understand
    if the loom has failed. Once diagnosed, then you'd need to look at
    making such a repair more permanent.
    Mike Dodd, Dec 3, 2005
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