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Thread: Generator yellow then to green once warm

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    Default Generator yellow then to green once warm

    First time post and love this forum. I have a 1993 M998 with the 6.5 NA. Recently, after I start the engine the voltmeter hangs in the yellow until it warms up a little and then climbs into the green. Voltmeter test at the batteries indicates an under charge in the yellow but once in the green itís the proper charge. Could this be slipping belts or voltage regulator? I tried to check a bunch of other threads without luck.

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    2 Star General TOBASH's Avatar
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    Welcome!!!

    Depending on your PCB, (protective control box), the glow plugs may be kept ON until the engine warms up completely. This electrical drain will reflect in lower voltage and amperage until the engine block warms up.

    The "yellow light" might also pulsate, (especially noticeable at night).

    The PCB is on the left, behind the starter switch, best viewed from under the dash and looking up and left. There will be a yellow or white or green sticker on it with writing. Take a picture of the label and post, and many of us will be able to tell you if your box is involved in this behavior.

    Not a big thing if your PCB is involved...just something to ignore.

    Best,

    T
    T.O.B.A.S.H - When we feel frustrated with those around us. LOL


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    Something else to check is the batteries. If the batteries or a battery is getting weak, while they will still be able to start the engine, the starting will draw them down more than fresh ones.

    Put them on a charger, then load test them. It is an easy thing to check and eliminates a possible problem.

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    And to pile on some unsolicited advice (since others beat me to the PCB comment and after-glow profiles): it's worth checking to see if you have a proper grounding harness in it, as bad or intermittent grounds in the electrical system will also cause similar problems now and down the road. It's an important "new to me" maintenance item, if the previous owner hadn't done it.

    Welcome to the fun!

    Bulldogger

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    Quote Originally Posted by Dank400ex View Post
    First time post and love this forum. I have a 1993 M998 with the 6.5 NA. Recently, after I start the engine the voltmeter hangs in the yellow until it warms up a little and then climbs into the green. Voltmeter test at the batteries indicates an under charge in the yellow but once in the green it’s the proper charge. Could this be slipping belts or voltage regulator? I tried to check a bunch of other threads without luck.

    What generator do you have? 200amp does not start charging right away...
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    Default PCB photo.

    Please see attached photo of my PCB and let me know what you think!

    D445B2E5-8E38-49CE-91FD-824022C2DF33.jpg

    Quote Originally Posted by TOBASH View Post
    Welcome!!!

    Depending on your PCB, (protective control box), the glow plugs may be kept ON until the engine warms up completely. This electrical drain will reflect in lower voltage and amperage until the engine block warms up.

    The "yellow light" might also pulsate, (especially noticeable at night).

    The PCB is on the left, behind the starter switch, best viewed from under the dash and looking up and left. There will be a yellow or white or green sticker on it with writing. Take a picture of the label and post, and many of us will be able to tell you if your box is involved in this behavior.

    Not a big thing if your PCB is involved...just something to ignore.

    Best,

    T

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    2 Star General TOBASH's Avatar
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    RWH likes smart start systems, and he is a great and reliable source of information.
    T.O.B.A.S.H - When we feel frustrated with those around us. LOL


    The Great Wall of China is regarded as one of the Seven Wonders of the World. What is wrong with The Greatest Country in The World building its own???

    1987 M1025 Slantback, 6.2 w/3 speed
    2017 Tesla Model X P100D
    2011 Tesla Roadster
    2003 Lifted Durango with steel bumpers
    1984 Toyota BJ-44 RHD
    Restoring 1975 Toyota Iron Pig

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    Quote Originally Posted by Dank400ex View Post
    Please see attached photo of my PCB and let me know what you think!

    D445B2E5-8E38-49CE-91FD-824022C2DF33.jpg

    Still haven’t answered question on what Generator you have...
    but that box is an S3, so no visible pulsed voltage drop for 2mins..
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    500C055C-B5E0-43AD-B247-52ACB8CED56A.jpgSorry about that! It’s a 60 amp generator..photo attached.

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    I was cruising around the other day and noticed the voltmeter was hanging in the yellow again. There also was a belt squeal under the hood for a few minutes. Once the belt stopped squealing, the gauge was in the green. Is it possible the belts are slipping or more likely my generator is seizing up and once it gets moving it charges better?

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