HMMWV Volts Jump Sporadicly

[Skinner23]

I noticed a few days ago after I started driving my voltage gauge was pegged to the max and it was in the green while warming up. Turned the lights off and back on, let off the gas and gave it some gas and it never moved. Just staid pegged. Soon there after went back to the green.
Yesterday afternoon left the house and the exact same thing happened. Let it warm up for 10-15 minutes while loading up to go hunting hoping that would help but no luck. Finished hunting that night and it never did it on the way home.
Left to go hunting this morning and it happens again. Only reason I noticed is because it was still dark so I had my head lights on and all the sudden they were super bright. Looked down and the volt gauge was pegged to the max again but only briefly. Happened two more times each for about 9 seconds.
This tells me it's not the gauge but that it is in fact surging sporadicly.
Any thoughts on the cause?? Appears to do ok with it but don't want anything getting fried. Only had it a month or so, so I'm still figuring out it's quirks.
Thanks


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[Bulldogger]

Start simple: check all battery and generator connections first. Take apart, clean and refit, if you have the time to be that thorough. Just tighten them all, if not. Be sure to check the battery connections on the back of the battery box by the starter, not just the ones inside.

All that said, in my personal experience it was the regulator causing the kind of surges you mention. However, I found some loose connections I hadn't noticed before when digging deeper into why mine failed. Tightening all the +12V cables and wires is a cheap fix if it's a loose connection making your gen/reg mad.

Even if it is the regulator or the generator brushes, you'd want the replacements to have a good start in life, so checking all connections is still important.

Have you installed a grounding kit? Bad grounds is a notorious problem on these rides. That's another set of connections to trace and tighten, when you are so inclined, whether you install supplemental grounds or not.

Good luck!

Bulldogger

 

[Skinner23]

Start simple: check all battery and generator connections first. Take apart, clean and refit, if you have the time to be that thorough. Just tighten them all, if not. Be sure to check the battery connections on the back of the battery box by the starter, not just the ones inside.

All that said, in my personal experience it was the regulator causing the kind of surges you mention. However, I found some loose connections I hadn't noticed before when digging deeper into why mine failed. Tightening all the +12V cables and wires is a cheap fix if it's a loose connection making your gen/reg mad.

Even if it is the regulator or the generator brushes, you'd want the replacements to have a good start in life, so checking all connections is still important.

Have you installed a grounding kit? Bad grounds is a notorious problem on these rides. That's another set of connections to trace and tighten, when you are so inclined, whether you install supplemental grounds or not.

Good luck!

Bulldogger

Thanks for the tips!! No grounding kit yet. It's on the to do/wish list as I'm doing little things here and there on the new rig.


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[orgnal]

I noticed a few days ago after I started driving my voltage gauge was pegged to the max and it was in the green while warming up. Turned the lights off and back on, let off the gas and gave it some gas and it never moved. Just staid pegged. Soon there after went back to the green.
Yesterday afternoon left the house and the exact same thing happened. Let it warm up for 10-15 minutes while loading up to go hunting hoping that would help but no luck. Finished hunting that night and it never did it on the way home.
Left to go hunting this morning and it happens again. Only reason I noticed is because it was still dark so I had my head lights on and all the sudden they were super bright. Looked down and the volt gauge was pegged to the max again but only briefly. Happened two more times each for about 9 seconds.
This tells me it's not the gauge but that it is in fact surging sporadicly.
Any thoughts on the cause?? Appears to do ok with it but don't want anything getting fried. Only had it a month or so, so I'm still figuring out it's quirks.
Thanks


Sent from my iPhone using Tapatalk

To me it sounds like a quirky alternator. Put a voltmeter at the battery terminals when this is happening and see what voltage the alternator is putting out for those 9 seconds. If it is much more than 28v your batteries may get fried. Worst case scenario, you will need a new alternator. Best case scenario, this will keep happening and not fry your batteries.

McReddy

 

[NDT]

To me it sounds like a quirky alternator. Put a voltmeter at the battery terminals when this is happening and see what voltage the alternator is putting out for those 9 seconds. If it is much more than 28v your batteries may get fried. Worst case scenario, you will need a new alternator. Best case scenario, this will keep happening and not fry your batteries.

McReddy

Agreed, it's your alternator throwing pvc's. About to have an attack. Worst case it takes your high dollar start box with it.

 

[gimpyrobb]

I don't own a hmmwv so I don't know. Is it that hard to pull the alt and have it tested? Everything that could blow up electrical wise, I wouldn't test it in the vehicle.

 

[orgnal]

I don't own a hmmwv so I don't know. Is it that hard to pull the alt and have it tested? Everything that could blow up electrical wise, I wouldn't test it in the vehicle.

It is not too bad to remove the alternator. There is plenty of space. Remove the small black plastic cover. Remove the wires. Remove the bolts / nuts. It took me a while the first time; I was being extra careful not to f*** up anything.

McReddy

 

[Dock Rocker]

It is not too bad to remove the alternator. There is plenty of space. Remove the small black plastic cover. Remove the wires. Remove the bolts / nuts. It took me a while the first time; I was being extra careful not to f*** up anything.

McReddy

Be ready when you take the bolts loose. It’s heavy as a mother.


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[Ephraim76]

Skinner I’m having the same issue.. did you figure out what it was?

 

[Skinner23]

Skinner I’m having the same issue.. did you figure out what it was?

It was the voltage regulator. Put a new alternator on and good as new.


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[Ephraim76]

It was the voltage regulator. Put a new alternator on and good as new.
Did you just replace the 60 amp alternator with a new 60 amp alternator? If so where did you buy yours from?

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Did you just replace the 60 amp alternator with a new 60 amp alternator? If so where did you buy yours from?

 

[Skinner23]

Did you just replace the 60 amp alternator with a new 60 amp alternator? If so where did you buy yours from?

I’ve haven’t had time to do it myself with traveling so much for work so I got a local guy to do it all for me who is very familiar with military trucks in general. So unfortunately I’m not exactly sure what type he used. The place I took it was Compucar in North Augusta, SC if you want to google them and give them a call. Ernie is super helpful and tons of knowledge!


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[DatGuyC]

Did you just replace the 60 amp alternator with a new 60 amp alternator? If so where did you buy yours from?

If you have a 60 amp alternator you can just get the voltage regulator, they screw onto the back. You just have to make sure you know exactly which alternator you have so you get the right one.

 

[papakb]

A word of caution playing with the alternator. That large stud on the output terminal is connected directly to the batteries, do not pass GO, do not collect $200. If you remove the small black cover that covers it and short it out your going to have your own 4th of July right there in the engine compartment. MAKE SURE TO DISCONNECT YOUR BATTERIES BEFORE DOING THIS!!