Problem with my HMMWY

[MOHRTEC]

Hi guys,

i'm from germany and ask for your help with a problem.

When i start my humvee the display of the oil pressure immediately shows 120. When i drive 2 minutes the vehicle temperature shows 240 degrees. I opened the hood. The connection from the engine to the radiator is very warm. I don't know where the error is. I disconnected the oil pressure connection but the display still shows something. The same at temperature. The generator display shows nothing. sometimes it works, sometimes not. I briefly turned off the engine at the traffic lights yesterday and suddenly the oil pressure shows only 60. The next time i turn off the engine and then turn it on again it will show me 120 again.

What can i do?

-Moritz

 

[Retiredwarhorses]

Find a good hmmwv mechanic or download the TM’s to properly TS the issues.
sounds like you just received your truck? Did you buy from reputable person or business?
i see many exported trucks as a way for guys to dump marginal truck.

 

[Milcommoguy]

Many will say add a ground wire kit. IMO remove all the grounding connection points, wire brush (real good) all connections and the metal attachment points. Get the bolts too or replace. When done spray or brush "red glyptal" coating. Search for the little bottle, about $14. paint in up real good.

Major ground points"
Shunt in and out
Starter stud
Engine block at rear
Alternator
Body behind fuel filter, in front of gauge panel. A little hard to find.
All gauges 4

Something to check:
Steering wheel column
All lighting ground returns on buckets and markers

While it can take time to hit all the spots, knowing there good now will save bigger headaches later on.

Think that's it? Could have miss one?

Old HumV's need TLC to chase out the electrical gremlines, CAMO

 

[MOHRTEC]

Find a good hmmwv mechanic or download the TM’s to properly TS the issues.
sounds like you just received your truck? Did you buy from reputable person or business?
i see many exported trucks as a way for guys to dump marginal truck.

I bought it directly from the army in Ohio and brought it to germany by ship.

I'm here for a pcs of advice because nobody in Germany is familiar with the car...

 

[papakb]

The gauges in the HMMWV, with the exce[tion of the voltmeter are current gauges and if you lose the ground to the panel they'll read high like yours. A poor ground wil cause them to read on the low side because it's opposing the flow of current thru the gauges. Check to make sure there is a good connection between the instrument panel and the ground stud on the firewall in front of the heater controls. The voltmeter is a single wire gauge that reads the output voltage of the alternator. Since it is displaying nothing it sure sounds like you have a broken ground in your truck. You could run a test wire from the panel ground to the current shunt in the battery box as a test.

Red glyptol tends to be permanant but I'm sure you can find something at Burklin that will work as an anti-oxidant.corrosion protector.

One of the easiers ways to check oil pressure is to "T" in a mechanical gauge right there at the back of the engine where the sensor lives. The temp gauge sender is in the left front cylinder head behind the alternator.

 

[Retiredwarhorses]

Number 1 reason the OP is maxed out I’ve seen is the wrong sender was installed during reset...the sender for the hmmwv is specific.MS24539-1
also, what OP gauge do you have...?

 

[DREDnot]

Another simple test to run is checking the voltage output from the batteries with the engine off, and from the generator when its running.

Just to confirm you are good there first.

I also agree that ground issues are likely with ALL the gauges geeking out randomly.

Cleaning ground and power connection points is a good practice on any new-to-you vehicle and you get to detail inspect it more thoroughly.

A home built grounding harness is easy to make and install and keeps a lot of problems like this from happening in the first place

 

[Retiredwarhorses]

Folks need to understand that a ground harness fixing anything, is masking a bigger problem...no US military hmmwv has a ground harness.

 

[dmetalmiki]

Do you know Tobia sin deusaldorf? He has a HUMVI and might be of help.
And in any case another comrade of the hobby for you in the E.U.
tobias.schlotbohm@gmx.de
As to," No earth kit solves an underlying problem the military humvees did not have them",
A well maintained original condition vehicle (Any) , Does not have an earthing problems, Simply because all the the origil wires conections and earthing ponts ARE in GOOD condition.
Now, Of course with age use and usage conditions, these electrical point DO gradually deteriate.
So, (Again). As outlined well previously, Clean, Clean, Clean,
OR!..( It is sound sense and worthwhile to,,) Replace or substitute them.
I certainly have (Had to) take off and make good the common earthing points on my trucks numorous times to get guages to work.
CHANGE the Temperatire and oil Pressure guages for mechanical 'Look allike' ones, Then, WYSIWIG!.
(What you see IS what you get! (Actually have)).

 

[DREDnot]

Folks need to understand that a ground harness fixing anything, is masking a bigger problem...no US military hmmwv has a ground harness.

True. But now that these things are 20+ years old they are having issues with corrosion, damage, and unknown amounts of questionable maintenance that render that original grounding pathways less than adaquate

 

[Retiredwarhorses]

True. But now that these things are 20+ years old they are having issues with corrosion, damage, and unknown amounts of questionable maintenance that render that original grounding pathways less than adaquate

like I said, your just masking a bigger issue. We don’t install them on ANY trucks in my shop nor have I seen one on a hmmwv in the military in my 27yrs.

 

[Milcommoguy]

It worked when it left the factory. Thirty years later... all the things and more stated have taken a toll.

Electrical FIX it, tires you can patch, CAMO

 

[Coug]

Folks need to understand that a ground harness fixing anything, is masking a bigger problem...no US military hmmwv has a ground harness.

I've seen you say this a few times. Not trying to argue with you about it, but what underlying issues other than just bad grounds would doing a grounding harness mask? I

 

[3jacks]

An electrical circuit does not care how or how many points to earth it has. Clean the grounds in the truck AND put a harness in...won’t hurt a single thing and can actually help. Your house has at least 2 and probably 3 points to earth...all connected. Nothing wrong with it.

 

[DREDnot]

I think what hes saying is that these things have dedicated ground wires from all points built into the harnesses.
For just this reason.

The main "underlying problem" would be a bad harness or compromised internal grounding path inside a component. The TM electrical trouble shooting will usually end at replacing the component or the wire that's bad...or just a new harness.

The ground harness mod is common in the jeep/automotive circles.
Usually dealing with lighting issues due to grounding problems arising from the body dependent grounding path.
Every jeep ive gotten that wasn't new has needed a ground harness for rear lighting reliability as they grounded through a now rusty body.

Not everyone can discect a wiring harness to find the culprit if its not as simple as a broken ring terminal somewhere visible....Even though thats the correct fix

 

[TOBASH]

When I got my HMMWV, my gauges did not work. I got the vehicle from someone who said he rebuilt and fixed most issues prior to sale. Maybe, but I think he was dyslexic. Several items were backwards and such.

I went through all gauge cluster wires with a voltmeter and found most of my wires were backwards, meaning polarity was attached incorrectly. Additionally, one light ground was corroded and I needed to bypass. Many connections were corroded, so I cleaned and then placed dielectric grease.

Also there is a main ground at the firewall that I re-grounded due to corrosion.

Bottom line, you need to ensure that your wires go to the correct gauges. Then you need to ensure they are connected with the correct polarity. Then you need to ensure they are all grounded properly.

Each wire is numbered with a metal crimp-on. Some of them get corroded and you need to clean so you can read the alpha numeric designation. You need to ensure each numbered wire goes where it needs to go.

Just because your HMMWV starts and drives does NOT ensure that the gauges to the dashboard are in the correct sequence.

ALSO, if your Cadillac valve is not functioning and the fan does not come on and off, that might account for a temperature over 200 degrees F.

Oil pressure is more typical to start at 60 and drop down.

It seems that your wires might go to wrong gauges if you disconnect sensors and the gauges still show readings.

If I was a betting man, I would think your wires to the gauges are not connected properly and/or are not grounded properly.

See if you can go to the TM/technical manual for each item and isolate which gauge wires go where. Then ensure your vehicle is set up properly.

I have a friend with a couple of HMMWV's and I was going to go to him to look at wires if I couldn't fix myself, but then I figured it all out. If you have a friend with a HMMWV, think about looking at his/her vehicle. In Germany, there are certainly a few people like you with HMMWV's. Problem is, COVID-19 virus might make people want to maintain social distancing for a while. [Note to future readers, 2020 was the year of the coronavirus pandemic].

Finally, Retired War Horses makes a good point in that a grounding harness is NOT meant for this issue and is not used my the US military. The grounding harness upgrade is meant for other issues.

MHO

T

 

[Retiredwarhorses]

I've seen you say this a few times. Not trying to argue with you about it, but what underlying issues other than just bad grounds would doing a grounding harness mask? I

i keep seeing people post here and on FB when some guy has a problem...Damn near almost any problem, “install a ground harness”, how bout go find the problem? What happend to fixing the problem?
Now, doing this 7 days a week, 365 days a years has taught me that if a ground harness fixes a proble, there is still a problem!, you didn’t fix the source, you addressed a symptom. Most electrical issues are in no particular order:
-poor grounds
-corrosion at terminals
-poor connections
-body grounds used for civilian accessories
-poor best practices applied on wiring installation
-use of cheap aftermarket parts not rated for 24v
-use of non OEM electrical components
-just being lazy, cheap and having a “it’s good enough“ attitude.

The Govt never issued an NSN for a ground harness, it’s something that came into exsitance around the first USMC trucks in 1999, those trucks were electrical nightmares in a lot cases due to corrosion.
i actually fixed a truck with said harness....that immediately made me go look for the source, and I did, it turned out to be a bad engine harness.