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Thread: Dmch alternator issue

  1. #1
    Member
    Join Date:  Jun 2018

    Location:  NY/PA

    Posts:    50

    My VIN:    17007

    Dmch alternator issue

    Just installed there alternator,when all
    Was said and done I now have this problem. I cant think of anything I did wrong that would case this issue https://youtu.be/_OWN-zleySwm.

  2. #2
    Senior Member
    Join Date:  Nov 2014

    Location:  Alexandria, VA

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    Appears to be more likely an idle issue...was the idle like that prior to your alternator swap?

  3. #3
    Senior Member
    Join Date:  Jun 2011

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    Belt slipping? Not tight enough?


    Sept. 81, auto, black interior

  4. #4
    Member
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    Quote Originally Posted by dmcnc View Post
    Appears to be more likely an idle issue...was the idle like that prior to your alternator swap?
    I did not have this issue prior to the swap. The previous alternator was oem and still working.i believe the belts are tighten properly being I put the stainless alternator adjuster on. If anything I was concerned I may of over tighten.Alternator appeared to be straight forward install: cleaned mounting bracket , 3 red bunch wires to alternator and single alternator wire to single wire from factory harness.Also needless to say when the fans kick on it gets worse.
    List of things I did at the same time

    Dmch starter
    Dmch alternator
    New interstate battery mtp-78
    Pressure regulator
    Oil change
    Remove catalytic convertor and replace with test pipe

  5. #5
    Senior Member
    Join Date:  Nov 2014

    Location:  Alexandria, VA

    Posts:    217

    You could do a voltage drop test between the alternator and the battery on both the ground and + sides of that circuit and/or reinstall the old alternator (is it a Motorola?) to see if the issue continues.

  6. #6
    AKA "The Goat" Michael's Avatar
    Join Date:  May 2011

    Posts:    3,761

    A slipping belt would be worse as the rpms rose. It looks like a dead battery to me but you said it was new.

    Get your mulitmeter and watch the voltage. Check it at the battery and at the alternator. If the battery is showing less than 12.8v while running, charge it and try again. It is possible you just got a bad alternator with a bad diode.

  7. #7
    Member
    Join Date:  Jun 2018

    Location:  NY/PA

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    Okay I will check voltage and report back. Sad was looking forward to taking it out tonight thinking with all the “upgrades” I would feel more confident driving it. Anyways prior to these installs, it would sometime chase idle for a couple of second on start up when smooth out perfectly. When first started after install it immediately sounded totally different. Okay out to the garage .....

  8. #8
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    Quote Originally Posted by Dontilgon View Post
    I did not have this issue prior to the swap. The previous alternator was oem and still working.i believe the belts are tighten properly being I put the stainless alternator adjuster on. If anything I was concerned I may of over tighten.Alternator appeared to be straight forward install: cleaned mounting bracket , 3 red bunch wires to alternator and single alternator wire to single wire from factory harness.Also needless to say when the fans kick on it gets worse.
    List of things I did at the same time

    Dmch starter
    Dmch alternator
    New interstate battery mtp-78
    Pressure regulator
    Oil change
    Remove catalytic convertor and replace with test pipe
    I bet the test pipe has caused the idle hunt. You need to adjust your mixture now.

    The idle hunt is probably causing a low voltage condition when the idle drops below 700 RPM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #9
    Member
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    14.9 at the battery but It obviously fluctuates with the idle.Interesting thing I started it this morning and it idled perfectly for a good minute or two,opened up the engine bay and noticed the cold start unplugged. Plugged back in and it stayed the same. I noticed has the car started heating up it seemed to have gotten worse and then it was back to its old tricks

  10. #10
    Delorean Guru
    Join Date:  May 2011

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    Some hunting is normal. To reduce it you must make each cylinder as balanced (equal) to each other as possible. You also have to find and fix all vacuum leaks. Your car sounds pretty normal.
    David Teitelbaum

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