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ECU repair for A/C failure following FSM Troubleshooting guide.

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    ECU repair for A/C failure following FSM Troubleshooting guide.

    Hello.

    If you follow the FSM trouble shooting guide to Diagnosis for "No Condenser fan no magnetic clutch operation" on page U-12 and have a failure at STEP 4 it tells you to Check ECU operation.

    If you would like to save $100 and not buy a spare ECU pop that boy out and the most likely culprit is Resistor R842 which is the first component from the 1J pin.

    Click image for larger version

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    The other lead in resistor is from the 1Q pin is R505 but is connected to the AC switch so that should blow up first it is a film 666Ω if you did manage to blow it.

    I had the R842 resistor blown in 2 of the ECU's I have. On a non-blown one I measured the value at 4.1Ω and pulled the part number to confirm that value and determine its wattage rating.
    The only visible number on the part I can make out is
    3R9J

    There are two major resistors with that code
    RS-1-3R9J and RS-2-3R9J

    They are Metal Oxide resistors rated at 3.9Ω and a 5% tolerance.

    The different number there is the wattage. The other physically similar resistors are 1w.The 2w labeled resistors are about double the size. I would not recommended over watting these as this resistor is protecting an IC down the line if I pathed it proper.

    Any 1 watt Metal Oxide resistor rated at 3.9-4Ω and a 5% tolerance should work fine. As I can only find those verbatim ones for sale in bulk. And do not need 50 of them.
    Beater=/= Sleeper

    Originally posted by kozzman555
    kitty, you are a hilarious woman
    Originally posted by HopelessCow
    there is one thing i dunno what is that call,a thing look like a gun, u press the button and stick to the metal and it makes firework, do i need that thing?and what s the philip head screw drivers?
    Using Linux for anything serious besides server or software dev is like using a tin can and a string for telecommunications.

    #2
    Good information. You can see the heat discolouration on the resistor body.

    There are a few in stock at digikey in single qty.
    Last edited by SgtFox; 02-18-2021, 09:47 PM.

    Comment


      #3
      Amazing work Kitty. This is the best forum on the internet, and posts like this one are the reason why. Your contributions are appreciated.
      1990 Protege 4WD
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      2 4 R


      Seeking: Canadian 4WD seatbelts.

      Comment


        #4
        Originally posted by SgtFox View Post
        Good information. You can see the heat discolouration on the resistor body.
        Yeah, it is pretty blatant once you compare it to the same class resistor near it.


        Originally posted by me109 View Post
        Amazing work Kitty. This is the best forum on the internet, and posts like this one are the reason why. Your contributions are appreciated.

        Thanks.
        Beater=/= Sleeper

        Originally posted by kozzman555
        kitty, you are a hilarious woman
        Originally posted by HopelessCow
        there is one thing i dunno what is that call,a thing look like a gun, u press the button and stick to the metal and it makes firework, do i need that thing?and what s the philip head screw drivers?
        Using Linux for anything serious besides server or software dev is like using a tin can and a string for telecommunications.

        Comment

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