Generator yellow then to green once warm

[Dank400ex]

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.

 

[TOBASH]

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

 

[Scrounger]

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.

 

[Bulldogger]

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

 

[Retiredwarhorses]

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...

 

[Dank400ex]

PCB photo.

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

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

 

[TOBASH]

RWH likes smart start systems, and he is a great and reliable source of information.

 

[Retiredwarhorses]

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

View attachment 762114

Still haven’t answered question on what Generator you have...
but that box is an S3, so no visible pulsed voltage drop for 2mins..

 

[Dank400ex]

Sorry about that! It’s a 60 amp generator..photo attached.

 

[Dank400ex]

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?

 

[NormB]

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?

Might be brushes, or the regulator on the generator, OR bad connections.

Oh, and a shot of belt dressing spray and/or check belt tension.

Anyone else?

 

[Bulldogger]

In my experience, random changes can be dirt in your brushes and a one time thing, or your batteries could be struggling to start the motor and the yellow represents the alternator pushing them back up, or bad connections. I thought my connections in the battery box were good and was confused about strange readings, then I noticed there is a connection in the outside of the box, near the starter. Basically the post that the +24V cable goes to has two ends, and both need to be tight.
So check your connections and if you have the time and ability you could also pull your batteries and have them tested.

In my 3 years of ownership and experience the yellow green thing is only a problem if it happens more than once in a while.

Bulldogger

 

[155mm]

check the alternator bracket on the bottom adjustment slide, make sure its not broken. also verify the rear support to manifold is present. and the dirty word spacer is between the gen and mounting bracket.

 

[MarkM]

I had the same issue and with mine it was the regulator.

Mark

 

[155mm]

If it ends up being a regulator or bearing, read this thread.


https://www.steelsoldiers.com/showthread.php?145991-60-amp-rebuild-I-got-stupid&highlight=