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2008 LTMV goes into over charge dash shuts off

R

Ronmar

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Yes, you can delete the LBCD regardless of using 2 or 4 batteries. You can also simply unplug it... It does control the charge system failure light, but it only does so if it sees low voltage above a certain alternator RPM. The LBCD's main function is as a polarity protection device. its secondary functions are to drive the charge sys failure lamp and to disconnect the expensive alt from the grossly oversized battery before it kills the alt. If you disconnect 2 of the 4 batts, it no longer needs to be able to perform a remote disconnect so you could simply unplug its cannon plug if it is erroneously reporting an alternator not providing 14.1/28.2V at high RPM...

If of course the alt 24V isn't OK, that will have to be addressed.

If the AOP is bad, I would simply delete it and replace the tiny .25cu/in single acting hand pump with a larger 1.5cu/in dual acting prince wolverine hand pump... ~$250 in parts, 2-3 hours to fab a mount for the new pump and plumb it to the valve... I use one of these pumps and I can raise the cab faster than the AOP used to(videos on youtube, username Rronmar)

Good luck and good hunting...
 
MatthewWBailey

MatthewWBailey

Thanks for this site. My truck runs great now!
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MGVFD said:
Well I guess a special. I am not a mechanic not am I paid. I work on this truck when time permits to help the station. So I read some of these thread and it is still clear as mud. If my post offend you or anyone else sorry. I am trying to figure this out so we can get these trucks back on the road. I reread the threads. I am not sure if you can delete the lcbd with a two battery setup? Our station doesn't have a big budget so if I can save it $700 then that is a win. We have to get batteries regardless. Most likely the ones in it are out of date.

Thank you for your patience.
Click to expand...
After reading @GeneralDisorder 's thread on the capacitor carnage, I deleted my LBCD completely, physically, figuratively, literally. Peace of mind

It's a complete and utter waste of time and energy. Mine was fully operational and I sent it to another member who wanted it, along with the disconnect relay.

You have to bolt the line and load leads together after removing the LBCD. I put polarity protectors in the PDP as @hike has done to perform the polarity protection. I only have 2 batteries to make 24v. My alt is straight 24v and cost $170, and operates the "charging system" light (@Ronmar showed how). 12v comes from a Victron power supply. Simplicity has its uses. I'm putting a shorting block across the manual disconnect terminals for security purposes (update in a few days) but leaving that device installed.
 
hike

hike

—realizing each day
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MGVFD said:
Well I guess a special. I am not a mechanic not am I paid. I work on this truck when time permits to help the station. So I read some of these thread and it is still clear as mud. If my post offend you or anyone else sorry. I am trying to figure this out so we can get these trucks back on the road. I reread the threads. I am not sure if you can delete the lcbd with a two battery setup? Our station doesn't have a big budget so if I can save it $700 then that is a win. We have to get batteries regardless. Most likely the ones in it are out of date.

Thank you for your patience.
Click to expand...
I certainly didn't mean to make you feel bad, My mistake, please forgive me. I just wanted to point you to the right info.

@Ronmar gave you great advice, though reviewing the write up you attached the $700 (EMS300-1224-D-00) part listed is the remote battery disconnect which is directly inward from your manual battery disconnect, not the LBCD under the spare, which is much more expensive I expect. If the write up shared is correct about the issue, unplugging the LBCD alone likely will not solve the issue. When we removed our LBCD, we also removed the remote battery disconnect (listed $700 part) as it is controlled by the LBCD, and two batteries. When reconnecting the two remaining batteries to provide 12v and 24v: bat1+ goes to manual disconnect 24v; bat1- goes to bat2+; bat2+ goes to manual disconnect 12v; bat2- goes to main ground and starter. I was concerned about the battery balancing while charging.

As @MatthewWBailey mentioned we next added a 24v alternator and Victron 24/12v converter to run our 2003 M1078A1. Though we did not add diodes at the PDP.

If you wish to just replace the $700 part listed we have a gently used one we bought new last fall and we'd be glad to work out a deal with a VFD. We also have a well used LBCD and dual voltage 100a alternator. PM if desired?

Where in Texas are you all?
 
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MGVFD

MGVFD

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Thank you all. We are in Cumby Texas just East of Greenville. Unincorporated Miller Grove Station 13. I don't feel bad. Just trying level set my experience level. I've worked on car and light trucks. This is my first diesel and large truck to work on and I get lost in the terminology. I'll post up pick when the new truck arrives. We had to be able to make a decision to accept the truck with the issues or not. Y'all's information has been valuable. TY
 
G

GeneralDisorder

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The part they listed is the disconnect relay (not the LBCD) - it may or may not actually be bad. There is a PS magazine article on the older disconnect relays with instructions on how to address a common wiring issue with them:

www.psmagazine.army.mil

M1078A1 FMTV: Culprit for Cab Power Loss

Dear Editor, my unit has had some issues with our M1078A1 FMTVs losing all cab power. The culprit is the battery disconnect relay assembly going bad. Here's a quick and easy fix...
www.psmagazine.army.mil
 
MGVFD

MGVFD

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Ronmar said:
OK, that device you pictured is the remote battery disconnect relay module. it is controlled by the LBCD, or a manual switch below the drivers dash(red guard switch cover). The LBCD monitors the alternator output and disconnects failed batteries from the alternator if the alt appears overloaded. it should light a batt disconnect light in the dash when that relay opens/disconnects the batteries. the LBCD and this relay was a band aid to help save the undersized alt. from the oversized battery bank when it overloads the alt. if you have new batts, I would disconnect the control cable from the LBCD until you can evaluate what exactly is going on, as it shouldn't activate until the alt passes 1500 RPM. You can access the LBCD module by lowering the spare tire and unplug the cannon plug on the module. If it still clicks, you can unplug the control lead on that relay module itself...

Well if CB70 pops immediately, you need to lift the dash and unplug PX-15 on the back of the light switch and try it again. if it still pops CB70, the wire between CB70 and the light switch plug is shorted to ground. if it does not pop, the light switch may be bad. I know the pushbutton switch assemblies are sensitive to having a good ground, so you need to make sure its ground wire is properly making contact with chassis ground. They also fail far more frequently than the older 3 lever switches do:)
Click to expand...
I have replaced the push button switch with a three lever switch. All the lights come on except the headlights. I did the jumper wire across 30/87 on the headlight relay. Did the same with the brights. I see the bright light indicator kit in the dash. Still no headlights. Is there a power diagram so I can jumper and test at the headlight. Tried yesterday and could get any voltage across any of the three legs at the headlight.

Second issue is the dash loses power. The dash lights stay on but the odometer and other gages drop not power. Is there a diagram for the dash inputs?
Thanks
 
G

GeneralDisorder

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Check the cab to chassis ground on the passenger wall of the radiator tunnel behind the grill. I HIGHLY suspect that this is what damages the push button switches. Just had one fail on an A1P2 that had a 2v drop across the cab ground strap a few months ago. The push button switches went through a revision and now come with a warning that they MUST have a proper ground wire connection from the body of the switch to the dash. But if the cab ground is bad, which they often are, the light switches will still not have a "good" ground since the whole cab is not grounded correctly and the switch will fail and sometimes melt.
 
MGVFD

MGVFD

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Both headlights were bad. We received another LTMV from a DOD grant. I swapped the headlights out of it for now.
 
R

Ronmar

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About any 7” headlight can be made to work. Mine had none, i started with basic P6 halogens from the parts store at first then shifted to some halo ring leds. Common jeep part, so lots to choose from. You will need yo make some adapter pigtails from the 1/8” female banana plug ends on the wire harness to whatever light you put in…
 
MGVFD

MGVFD

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That is the new one. It is a 2003. We are getting it ready to paint and put a tank in it. We have the 6x6 which I started this thread it is a 2008. What is the issue with the xml tires?
 
MGVFD

MGVFD

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I read the blow out thread from 2023. We have a slim budget and a timeline/check list set by the DOD grant. To get this rig painted and in service or we lose the grant. I guess beggars can't e choosers. I will bring the tire issues up to our members. It'll be a hard pill since these tires are 500 or more a piece. Is there any manufacturer info y'all have regarding this issue? It would be helpful when I bring this up.
 
G

GeneralDisorder

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MGVFD said:
That is the new one. It is a 2003. We are getting it ready to paint and put a tank in it. We have the 6x6 which I started this thread it is a 2008. What is the issue with the xml tires?
Click to expand...
They were problematic when old. And haven't been manufactured since at least 2011. Sidewall failures on these trucks often result in a roll-over accident. Usually crush the cab - often with fatalities. The military won't mount any tires more than 6-7 years old for good reason:

www.psmagazine.army.mil

Logistics Management: Tire Shelf Life vs Service Life

Dear Editor, there’s been some confusion in the field about the difference between a tire’s shelf life and its service life. (Read on to discover the difference).
www.psmagazine.army.mil

Check the DOT date on them - though I can guarantee they are probably original and 20 years old. Rolling on 20 year old tires is asking for this:

crash.jpg

As for your 2008. This is what happened to my 2008 Goodyear MV/T tires. And they are considered BETTER than the XML:

IMG_20230927_161019.jpg

IMG_20230927_161036.jpg

IMG_20230927_161044.jpg
 
G

GeneralDisorder

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MGVFD said:
I read the blow out thread from 2023. We have a slim budget and a timeline/check list set by the DOD grant. To get this rig painted and in service or we lose the grant. I guess beggars can't e choosers. I will bring the tire issues up to our members. It'll be a hard pill since these tires are 500 or more a piece. Is there any manufacturer info y'all have regarding this issue? It would be helpful when I bring this up.
Click to expand...
Yeah unfortunately it is probably THE biggest safety issue on these trucks. You got a free militarized class 8 semi truck...... that just be the way the cookie crumbles sir.
 
MGVFD

MGVFD

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GeneralDisorder said:
Check the cab to chassis ground on the passenger wall of the radiator tunnel behind the grill. I HIGHLY suspect that this is what damages the push button switches. Just had one fail on an A1P2 that had a 2v drop across the cab ground strap a few months ago. The push button switches went through a revision and now come with a warning that they MUST have a proper ground wire connection from the body of the switch to the dash. But if the cab ground is bad, which they often are, the light switches will still not have a "good" ground since the whole cab is not grounded correctly and the switch will fail and sometimes melt.
Click to expand...
How do you access the top of the grounding strap? It seems to be behind the body mount. I ohm'd the strap it did ok there. I have a new issue with the light cluster thinking it is knight rider. The lights are going back and forth.
 
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