1987 M998 Battery Generator Gauge Bouncing in Red, Stays in Red while driving for few minutes

[Lit_Armo]

Hello I've been noticing lately on startup of my M998, while parked, the battery generator gauge will move into the center of the red, then bounce to the edge of green, and move back and forth between these two spots. My lights will flicker.

When driving, with foot on the pedal, it moves completely passed the red area even farther out passed it. And then after a few minutes of driving it will settle in the center of green and not move from there like it's fine. I put pictures of the places I saw the gauge move to in chronological order.

I have a 6.2L engine, and no mods have been done to the engine. Hoping someone could please point me in the right direction to fix this.

 

[Mogman]

Most likely you have a 60A alt and the regulator is going wonky
It will toast a good set of batteries so you really should attend to it now.
Of course you should have put a volt meter on the batteries to confirm yes?

 

[Lit_Armo]

Most likely you have a 60A alt and the regulator is going wonky

Does my alternator have the model visible so I can order the right regulator for it? Or how can I confirm with regulator to get?

I put the voltmeter on both batteries one + and other -, then that’s the number? It should be how many volt? Thank you

 

[Mogman]

It should, get a set of brushes while you are at it.

 

[Lit_Armo]

It should, get a set of brushes while you are at it.

Thank you I'll check

 

[SmartDrug]

I think it’s your glow plugs being cycled on. If I just started my HMMWV and start to drive before they’re done cycling (60-90 seconds on a cold start), I will see this, too. I let it go through the standard warm up and everything is normal. I have the 200a Gen on an A2.

 

[Mogman]

I think it’s your glow plugs being cycled on. If I just started my HMMWV and start to drive before they’re done cycling (60-90 seconds on a cold start), I will see this, too. I let it go through the standard warm up and everything is normal. I have the 200a Gen on an A2.

Yes the first sentence in his post is normal this is called afterglow, but not the pegging of the gauge in the red.
Regulator failure is EXTREMELY common with the 60A alternator, this is one reason many convert to 100/200A alternators.

 

[SmartDrug]

Yes the first sentence in his post is normal this is called afterglow, but not the pegging of the gauge in the red.
Regulator failure is EXTREMELY common with the 60A alternator, this is one reason many convert to 100/200A alternators.

Mine does this if I’m driving during the “afterglow” period, when the plugs cycle off (Im guessing off, but don’t have alight rigged up yet), the battery gauge spikes into the red. If it’s not under load, it bounces between green and yellow until the afterglow is finished. I figured this was normal and that it took the regulator a moment to catch up with the changing electrical load. Once the afterglow is complete, everything seems normal, I haven’t had any issues with the electrical system in several years. I just don’t drive the truck until it has had a minute or so of warm up time.

Is this not normal?

 

[Mogman]

Bouncing between green and yellow is normal, pegging the needle to the right is not. it might get into the red as the needle over swings but again not pegged to the right.
This is why he needs to put a meter on the batteries or the output terminal of the alternator to see what is actually happening as the factory gauges are not very accurate.
But again pegging to the right for a "few minutes" or even a few seconds is not a good sign., especially for the 60A which is prone to frequent failure.

 

[SmartDrug]

Good deal, I should probably check mine as well. I think it’s just the swinging in the direction that causes it, but it is only momentary and it’s definitely not pegged in my case.

 

[Coug]

If it's going into the red at all, it's usually a bad regulator, but there's a slight chance it could also be a bad battery.

 

[TOBASH]

Always double check with an accurate multimeter

 

[Lit_Armo]

Bouncing between green and yellow is normal, pegging the needle to the right is not. it might get into the red as the needle over swings but again not pegged to the right.
This is why he needs to put a meter on the batteries or the output terminal of the alternator to see what is actually happening as the factory gauges are not very accurate.
But again pegging to the right for a "few minutes" or even a few seconds is not a good sign., especially for the 60A which is prone to frequent failure.

An electrician doing my sound system checked with a voltmeter and it’s going up too high. My new Phosqate radio says “high voltage” but only in the first few minutes. I think it’s the “afterglow” mentioned earlier. When I wait a few minutes for the bouncing to stop I don’t go into the red while driving anymore. Until I change the regulator I’ll just wait for a good warmup of the car.

 

[Mogman]

An electrician doing my sound system checked with a voltmeter and it’s going up too high. My new Phosqate radio says “high voltage” but only in the first few minutes. I think it’s the “afterglow” mentioned earlier. When I wait a few minutes for the bouncing to stop I don’t go into the red while driving anymore. Until I change the regulator I’ll just wait for a good warmup of the car.

If your radio is reporting high voltage then you should fix it before using it any more, the afterglow causes the voltage to drop at idle below normal but there should be no reason for it to go above normal, the longer you wait the more possible damage can be done, besides the fact it will likely fail as you are driving frying your new radio along with the batteries and putting you on the side of the road, if you have a 60A alt. it is not a matter of if but when it will fail, as soon as they act up it is time to act.
But of course it is entirely up to you.

 

[Coug]

Look at it this way.

For a 60 amp, you can spend the $100 or so on a new regulator and brushes, and install yourself.

If you decide to wait until it completely fails, you could spend $600+ on a new start box, a couple hundred on new batteries, and even more on anything else that gets damaged by the failure, and then spend the $100 for the voltage regulator and brushes.

It doesn't matter if it's afterglow or anything else, it should NEVER go up into the red.


You asked our opinion on it, and everyone agrees that there is an issue and you should stop using it until you get it resolved.

 

[Lit_Armo]

Look at it this way.

For a 60 amp, you can spend the $100 or so on a new regulator and brushes, and install yourself.

If you decide to wait until it completely fails, you could spend $600+ on a new start box, a couple hundred on new batteries, and even more on anything else that gets damaged by the failure, and then spend the $100 for the voltage regulator and brushes.

It doesn't matter if it's afterglow or anything else, it should NEVER go up into the red.


You asked our opinion on it, and everyone agrees that there is an issue and you should stop using it until you get it resolved.

If this is going to turn into a big problem like that, I want to get it resolved asap. If I get a new 100amp alternator is it plug and play? Should I just get the regulator or get a new alternator like the 100amp or is the 200amp possible?

 

[Mogman]

Nether is plug and play, with the 100A or 200A you will have to run a larger charge wire from the alt to the batteries, also both the 100 and 200A are dual voltage so you would want to run a second charge wire that keeps the batteries balanced and would allow to draw 12V from the center battery, I am assuming you are already doing this with your sound system, without the dual voltage alternator you will quickly ruin the batteries as the power you pull from the 12V connection causes one battery to over charge and one to under charge, with a single voltage alternator you must run a 24v/12v converter to operate 12V equipment
The 200A would also require changing the mounts etc. a kit is available and surprisingly quite affordable.
The alternator you have now if it is a 60A (you have not confirmed this) could be 25 years old, the 60A does have a reputation of failure but part of that is their age, unless you need the extra amps rebuilding the 60A is a good way to go, I have not heard of many issues after they are rebuilt.

 

[Coug]

As Mogman said, the 60 amp does just fine once rebuilt. It's just an older design so it requires more maintenance, but for the cost of changing out to a 200 amp you can rebuild the 60 amp dozens of times.
You could also change out to a civilian 24V alternator. Does take a little fabrication, and the alternator does cost more up front than the 60 amp rebuild, but you do get a much newer design and fewer worries.
I think at least one vendor sells a kit to change out to a civilian 24V alt, but I've never really looked into it.

As was said, only real downside is the batteries don't have anything to balance them, but there are many balancers out on the market; some very cheap, others much better quality.
One good quality example

Battery Balancer - Victron Energy

Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.

www.victronenergy.com

 

[Lit_Armo]

Nether is plug and play, with the 100A or 200A you will have to run a larger charge wire from the alt to the batteries, also both the 100 and 200A are dual voltage so you would want to run a second charge wire that keeps the batteries balanced and would allow to draw 12V from the center battery, I am assuming you are already doing this with your sound system, without the dual voltage alternator you will quickly ruin the batteries as the power you pull from the 12V connection causes one battery to over charge and one to under charge, with a single voltage alternator you must run a 24v/12v converter to operate 12V equipment
The 200A would also require changing the mounts etc. a kit is available and surprisingly quite affordable.
The alternator you have now if it is a 60A (you have not confirmed this) could be 25 years old, the 60A does have a reputation of failure but part of that is their age, unless you need the extra amps rebuilding the 60A is a good way to go, I have not heard of many issues after they are rebuilt.

This is my alternator in the attached I’m not sure which amp it is. The electrician who did the sound system said he could do a converter or just use 1 battery, I didn’t want to wait for the converter to ship so he didn’t go that route but I’m going to go back so he puts the 24v/12v converter.

 

[Mogman]

This is my alternator in the attached I’m not sure which amp it is. The electrician who did the sound system said he could do a converter or just use 1 battery, I didn’t want to wait for the converter to ship so he didn’t go that route but I’m going to go back so he puts the 24v/12v converter.

Yes that is a 60A, you also have a GEP engine that is very good!!