Short circuit reading with icarsoft OBD MBII

Discussion in 'GL-Class' started by Lauderdaler, May 24, 2017.

  1. Lauderdaler

    Lauderdaler New Member

    Throwing code of ac compressor short circuit., A9 component 9004 DTC,

    There's only the one painfully simple plug..

    Would this genetic desription be including relays. Fuses, or some sensor or what?
    The compressor is a new installed replacement, and I've tried to recharge as directed to via this forum, but it won't engage due to the lack of r134, but to introduce the Freon, the compressor must be ..., on. Correct?

    Further,... This only diagnostic hint is the vauge 'compressor short circuit '

    Coincidentally, while not overheating, the smooth running of the truck is now a near stall at stopping, and a jerky latency when turning and decelerating off a highway for instance. At traffic lights same loss of power at most inopportune moments.

    I holding hope that by short its referring also to the relay or fuse designed to block and dismiss such electrical spikes or drops,,, I had thougt it was.

    In any event, any intelligent insight to point to is well appreciated ,

    What it could be from
    Where to look
    What to look for
    Which location
    Which designation in boxes.

    Thank you all kindly
  2. laberia

    laberia Member

    I would check the wire that feeds 12 volts positive to the compressor. It is possible that it is cut. Have had this happened before and had to re-route new wire.

    You can charge the system with the compressor off and it will kick in when it reaches the minimum required pressure in the sytem. But yours isn't going to kick in because the compressor is not going to get power.

    I would find the wiring diagram for your car and check continuity of the wire that goes to the compressor.

    That's the first step. Maybe take a few pictures to post here as you troubleshoot this problem.
  3. Lauderdaler

    Lauderdaler New Member

    Thanks for the suggestion, and I'll surely share this event and document my learning curve so others might avoid some of the pitfalls faced by the unknowings like myself.

    I did infact examine the connection on the compressor, the plug is for two wire connection, I noticed only the 12v red, with the blk pigtaled to ground on the compressor body itself. The wrestle of install by a duffer, I thought the same as you kindly confirmed can and does, even has, happened and in this case, the simplest and most logical and intuitive suspects MAY be the culprit.

    My question going into this next step is whether or not I should remove the thing and do the repair or to,confirm it is a skinned wire incidentally?
    Is it possible to just remove the plughead, slide in some heat shrink insulation, then just reconnect the plug and test for continuity... ?

    Looking ahead, I'll beg of you one,more answer please,... When recharging, I'm seeing everyone warn to stop adding if the low side pressure goes North of 100psi, give or take...
    So I did., I mean I have,.done, but I wait, with running and air on max...then try again, seeing same red high pressure warned to not exceed.

    What am,i missing here... What am,i not doing or doing but doing incorrectly?
  4. laberia

    laberia Member

    You can remove the positive wire and test for continuity. You can also feed a 12 volt to the a/c compressor for two seconds to see if the compressor itself will engage. The engine should be running if you try this and don't keep it connected more than two seconds.

    Yes don't over charge it. The compressor should kick early. Depending on the gauge the arrow will be on the low side of the green / ok range. You shoudn't go into red.

    If you get the a/c working and the sytem charged properly, you may notice that the low pressure may go into the red zone when engine is turned off. That's is ok. It shouldn't be on red if the engine is running.

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