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Thread: 4amp draw- high pitched whine from engine compartment- ignition off

  1. #11
    Member gluaisrothaii's Avatar
    Join Date:  Sep 2019

    Posts:    90

    Quote Originally Posted by DMC-81 View Post
    Hi Ken,

    That is correct. I connected the brown wire to get rid of the flashing test sequence with the ignition on, but not started. There is more info here: http://dmctalk.org/showthread.php?12181-DMCH-alternator .
    Thanks! Read through that....weirdly I do not have the flashing test sequence. I wonder if there's a new rev of the regulator.

    Best,
    Ken
    1981 DMC 12- Black
    VIN 46**
    Alameda CA

  2. #12
    Senior Member
    Join Date:  Nov 2014

    Location:  Alexandria, VA

    Posts:    278

    Quote Originally Posted by gluaisrothaii View Post
    Alternator would be annoying. It's brand new from DMCH. 300 miles. Whine was there with the engine off.

    Just to clarify- alternator is topping battery off easily while driving, and running the lights etc, and the vehicle runs just fine. When turned off there's (sometimes) a real 4 amp electrical load that is depleting the battery. Something like a stuck relay. Whatever is consuming the power makes a high pitched whine in the engine compartment and doesn't show any signs of doing anything useful with the power.
    I had the same issue with the DMCH alternator - it's more of a high frequency noise the engine was off. It killed a battery or two before I figured out it was the alternator. I would either get it replaced or go for another option.

  3. #13
    Member gluaisrothaii's Avatar
    Join Date:  Sep 2019

    Posts:    90

    Quote Originally Posted by dmcnc View Post
    I had the same issue with the DMCH alternator - it's more of a high frequency noise the engine was off. It killed a battery or two before I figured out it was the alternator. I would either get it replaced or go for another option.
    Wow! Thanks for that. I'll give them a call right now.

    Ken
    1981 DMC 12- Black
    VIN 46**
    Alameda CA

  4. #14
    Member gluaisrothaii's Avatar
    Join Date:  Sep 2019

    Posts:    90

    Looks like the feed through the #191 bulb in the panel results in a 3 volt signal to the +L line on the alternator. Playing around with a potentiometer I was able to pull the alternator regulator online with a 0.4 volt signal- that's a low as I could go with the pot I had on hand (turned all the way down with a 1.5AA battery as the supply). It might come on with less that that. Seems like the alternator might be a little sensitive to something like a bad ground holding the voltage up on that feed line...
    1981 DMC 12- Black
    VIN 46**
    Alameda CA

  5. #15
    Senior Member - Owner since 2003 Patrick C's Avatar
    Join Date:  May 2011

    Location:  Northern Michigan

    Posts:    1,098

    My VIN:    1880

    Club(s):   (DCO) (DCUK)

    I had this EXACT problem with my DMCH alternator this fall! I went out to the garage and could hear a high pitched whining coming from the engine bay. I tried a lot of troubleshooting, but the whining noise seemed to go away on its own, but Iím not confident itís gone for good.
    Patrick C.
    VIN 1880
    Modifications done to my car can be seen in this video: https://youtu.be/ncMjW2pI2e4

  6. #16
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
    Join Date:  May 2011

    Posts:    4,098

    My VIN:    None of your business you creepy psycho vin counter...get a life

    For what it's worth when my DMCH alternator quit a few weeks ago it had a whine to it but it still charged at higher rpm. Low rpm was nothing. (I don't recall hearing any noise when the engine was off however).
    I doubt I will never buy another alternator as long as these local guys rebuild it like they did this one. Almost 15v on the gauge at idle and in almost 11 years and 3 alternators I have never had the confidence to run the AC at night because with lights and ac fans, I would go into single digits.

    My advice (which I followed from another member) is have yours rebuilt by a reputable place. Try to find a rebuilder that uses American components and has been in business for some time.

    My rebuild cost $90.00 and it came back cleaned looking brand new and with a new pigtail.
    Last edited by Michael; 12-27-2019 at 10:30 AM.

  7. #17
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,938

    My VIN:    03572

    Quote Originally Posted by gluaisrothaii View Post
    Thanks! Read through that....weirdly I do not have the flashing test sequence. I wonder if there's a new rev of the regulator.

    Best,
    Ken
    That is interesting that the DMCH unit now does not flash the error code (If sense is no hooked up). I wonder if DMCH is stocking a new alternator or if the manufacture changed the regulator.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #18
    Member gluaisrothaii's Avatar
    Join Date:  Sep 2019

    Posts:    90

    Final update- new alternator installed

    All,
    Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.

    Best,
    Ken
    1981 DMC 12- Black
    VIN 46**
    Alameda CA

  9. #19
    Senior Member
    Join Date:  Aug 2018

    Location:  Virginia

    Posts:    583

    Quote Originally Posted by gluaisrothaii View Post
    All,
    Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.

    Best,
    Ken
    Lol, great service? Great service would have been sending a quality alternator the first time around
    DMCF rebuild 2008, Stage II, Eibach

  10. #20
    Senior Member - Owner since 2003 Patrick C's Avatar
    Join Date:  May 2011

    Location:  Northern Michigan

    Posts:    1,098

    My VIN:    1880

    Club(s):   (DCO) (DCUK)

    I wonder if this is a known flaw with the DMCH alternator. If mine is still doing this in the spring when I pull it out of storage, Iíll have to contact them for a replacement.
    Patrick C.
    VIN 1880
    Modifications done to my car can be seen in this video: https://youtu.be/ncMjW2pI2e4

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