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Thread: MSD 6AL Continuity between Red / Black wire

  1. #1
    Join Date
    Jul 2018
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    Default MSD 6AL Continuity between Red / Black wire

    I have an MSD 6AL that I've triple checked for wiring. I have good spark and it runs ok until things warm up. Then there is a slow degrade until the engine quits. Once things cool off the cycle starts over.

    I noticed when I start the engine, the stereo would stop playing. So I hooked up my meter to the battery. When the engine is not running I've got 12.4v or so. Once I start the engine, I get an erratic reading (18V up and down). Initially I thought it might be a bad ground. I checked all wires, cleaned terminals ... no change. Then I noticed I could touch ground anywhere with just one lead from my meter and get the same erratic reading. So I thought maybe something was shorted. I eliminating things from the system until I was down to almost nothing but the MSD. I disconnected the unit and hooked my ohm meter to the Red/Black battery leads. The meter goes straight to 0.

    Is there supposed to be continuity between those wires?

  2. #2
    Join Date
    Jan 2010
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    Brisbane, Australia
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    I think you should be looking at a bad alternator, overcharging at 18 volts.
    The MSD and the stereo are both dropping out from high volts.
    Gary
    Regards

    Gary

  3. #3
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    Jul 2018
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    Default

    Quote Originally Posted by Gaz64 View Post
    I think you should be looking at a bad alternator, overcharging at 18 volts.
    The MSD and the stereo are both dropping out from high volts.
    Gary

    I thought that at first. It's a points system with a stator, so I disconnected anything else that might send a charge back to the system.

    My main question is the black/red continuity. Somehow it doesn't sound right. I tried it again yesterday. It ran for about 5min then stopped. I tried the white wire test and there was no spark. Waited a while and tried again. Spark was very strong.

  4. #4
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    Jul 2018
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    Thought I would attach a photo to clarify what I am seeing. Does anyone know if this is normal?

    Hope this works!

    MSD.jpg

  5. #5
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    Your meter is on the 2 Megohm scale, so not accurate at all.

    Drop the scaling down towards 200 ohms until you see something on the meter.

    That is certainly not "continuity" as you say.

    Gary
    Regards

    Gary

  6. #6
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    Jul 2018
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    I thought continuity was any ability for current flow. I was expecting the +/- leads to be completely open.

    So I dropped the meter down until I got to 1X. I'm reading 4.3
    200.jpg

  7. #7
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    Default

    It reads 000 on the 2M ohm scale because the resistance is so small.
    That's why your meter has manual scaling, you need to select any appropriate scale.
    For continuity testing, you need the 200 ohm scale.
    Now it appears you have 4.3 ohms across the red black, which would mean at 12v, about 2.8 amps flows as soon as you connect the battery, so the module looks faulty to me as well.
    Certainly would be the cause of a battery going flat.

    Gary
    Regards

    Gary

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