1988 Humvee Voltage gauge, is this normal ?

[JoeJrTheBarber]

Evening,

My new to me 1988 Humvee has been running like a top since I have owned it for the past month or so. I have noticed though the voltage gauge likes to "jump" around while driving.

It is either in this position:


Or this one:



The truck never changes the way it's running / No power loss / headlites never dim or whatever while the truck is running. And the gauge doesn't flop back and forth, where it will sit in say the 1st pic position for awhile and then at random will move to the 2nd position. Is this normal ? Sign of something going or gone bad ?

Thanks as always for the help...

 

[NormB]

I'll go with "Bad Military Gauges and Wiring" for $500, Alex.

Just one word. DVM. Digital Volt Meter. Well, an acronym then, but what would a foray into military vehicles be without acronyms?

Find one. Learn to use it. I own a couple, one in my truck, one in my HMMWV (both Radio Shack auto ranging pocket models for convenience), one in my basement workshop, a Fluke 18B.

Your first step is checking the voltage at the alternator, after checking the manual of course.

I'm betting if you remove, clean/deoxidize and apply something like Deoxit to the terminals/connections on the alternator, batteries, dash panel meter connectors and use some Dow Corning 4 Electrical Insulating Compound to lube up/seal/protect the rubber Packard connectors, this will go away. Or it's the meter. Or regulator, but you'll need a DVM.

Last time I checked, Harbor Freight was giving them away with a coupon you can find online. Adequate for minor troubleshooting/continuity testing, voltage readings, cheap enough you won't worry about stepping on or losing.

Keep us posted.

 

[ZiggyO]

Do you have a 60amp alternator? I had this exact problem on my deuce years ago-- turned out to be crud buildup on the commutator/brushes-- I pulled off the rear cover/regulator from the alternator and hosed it out really good with electrical contact cleaner and it has performed perfectly ever since......

Z

 

[papakb]

If you have a multimeter you can connect it between pins T and X on the STE/ICE connector next to the shifter and read the alternator output voltage.

If it's stable there your alternator is probably OK and you may have a loose connection somewhere in the line to the voltmeter. If it's jumping there you should take a look at the alternator itself. This is a good time to check the ground stud behind the heater controls where the dash panel grounds.

I'd also suggest that you check the connections on the batteries and the feedthru stud where the battery power lead passes thru the transmission tunnel. Look for loose or corroded connections. If that all looks good get under the truck and follow the battery lead from the feedthru that runs to the starter. If that looks good check the 8 gauge lead that runs from the starter up to the output stud on the alternator.

 

[Mario]

Evening,

My new to me 1988 Humvee has been running like a top since I have owned it for the past month or so. I have noticed though the voltage gauge likes to "jump" around while driving.

It is either in this position:
View attachment 715864

Or this one:
View attachment 715866


The truck never changes the way it's running / No power loss / headlites never dim or whatever while the truck is running. And the gauge doesn't flop back and forth, where it will sit in say the 1st pic position for awhile and then at random will move to the 2nd position. Is this normal ? Sign of something going or gone bad ?

Thanks as always for the help...

Common 60Amp generator issue.

Sent from my SM-G955U using Tapatalk

 

[JoeJrTheBarber]

Common 60Amp generator issue.

Sent from my SM-G955U using Tapatalk

This might be a dumb question but where should the gauge sit in "perfect" working order condition ?

 

[98G]

This might be a dumb question but where should the gauge sit in "perfect" working order condition ?

The little white tick mark in the middle of the green.

In the world of 5ton trucks your symptoms foreshadow voltage regulator failure and the frying of electrical components. Not sure about it in the context of hmmwv.

If you haven't yet installed a grounding harness, I suggest that. It may or may not have any effect on your current problem, but it's cheap and easy and will ward off future evils...

 

[Mario]

...In the world of 5ton trucks your symptoms foreshadow voltage regulator failure and the frying of electrical components. Not sure about it in the context of hmmwv.

Same in the HUMVEE world.
Some have had decent luck changing just the voltage regulator.
Many choose to use this 'opportunity' to just upgrade to 200A unit and gain 12V output as a bonus.

Sent from my SM-G955U using Tapatalk

 

[papakb]

The white "tick" mark is 28 volts and usually the gauge sits just to it's left edge. Before I trusted it though I'd get a meter on the STE/ICE pins and verify the actual voltage. These gauges are not always that accurate.

 

[Mario]

This might be a dumb question but where should the gauge sit in "perfect" working order condition ?

Your second picture is it.
That's what happened to mine as well. Worked for little while, than started jumping to max.
I ended up buying 200A unit since I wanted 12VDC option without just using one battery.

 

[JoeJrTheBarber]

Same in the HUMVEE world.
Some have had decent luck changing just the voltage regulator.
Many choose to use this 'opportunity' to just upgrade to 200A unit and gain 12V output as a bonus.

Sent from my SM-G955U using Tapatalk

Best place to source one of these fancy 200A units ?

 

[BLK HMMWV]

Ebay or the parts for sale section on this board. or better yet post a WTB in the HMMWV section.
Also over on the parts wanted section on the G.503 forum under HMMWV.
Or you can send 86humv a PM on either forum.
BH

 

[Mario]

Best place to source one of these fancy 200A units ?

I got both of mine from 86humv

Sent from my SM-G930P using Tapatalk

 

[SarahJ]

The alternating voltage happens on mine as well. Just taken it apart and found the centre section of the load resistor coming out! Also there was a tonne of carbon dust in there as well.