A Little Help Would Be Appreciated.....

[GeneralDisorder]

Should be a 3116 by the year. What does the diagnostic port look like on the driver's side kick panel? The A0 trucks have a 54 pin analog diagnostic port. The A1+ trucks have a 9 pin J1939 digital diagnostic port.

All of them say exactly what they are on the valve cover. All options are inline 6 cylinder engines. 3116 is a mechanical engine with no computer. The other two are computer controlled.

 

[Ronmar]

It has an A0 idiot light annunciator panel...

 

[Rick_bagby]

Run a new ground cable from the batts negative to a sanded spot on the main frame rail. I would then run a temporary wire from the battery positive to the front terminal on the regulator. See if your voltage still drops out.

Gotcha Suprman, I will disconnect the CTIS wire from the E terminal on the voltage regulator and run a temporary hot 24 volt wire and see if it drops out.

 

[Rick_bagby]

It has an A0 idiot light annunciator panel...

Well, I guess that fits me. LOL. A0 idiot light annunciator panel??

 

[Rick_bagby]

So much help and great ideas to go to. I wish I had known of this website sooner. You guys are just awesome. Thank you.

 

[Ronmar]

My first step in troubleshooting an lmtv electrical. Check battery 12&24 to chassis ground, then check panel 12&24 at the round test points(A0) or batt test point Bolts(A1 panel). Panel test points should be 1/2v less than battery. ~12.3/25.2 with 12.8v on all the batteries.

Then turn on the main sw and check panel 12&24 again. And then battery again with sw on. Should be the same 1/2 volt difference with sw on with or without load applied. If it is not, you have a wiring issue between batts and power panel.

 

[coachgeo]

is top of engine (valve cover) yellow or black?

 

[Rick_bagby]

is top of engine (valve cover) yellow or black?

The entire engine is yellow

 

[coachgeo]

The entire engine is yellow

that rules out an Acert being swapped in it, so unless it is an odd animal (and it happens) its a 3116 (aka..... engine swapped in later up the road by military... usually have black valve cover) so you should have giant sticker on top of yellow valve cover.

//uploads.tapatalk-cdn.com/20171111/ea205030fbfe9bb61f274f0ed9b6447c.jpg

 

[ckouba]

So much help and great ideas to go to. I wish I had known of this website sooner. You guys are just awesome. Thank you.

My favorite thing is free stuff but I feel compelled to suggest that for very modest contribution, you can help make sure it stays around:

https://steelsoldiers.com/account/upgrades

It's probably the easiest ROI I have ever achieved.

 

[Rick_bagby]

Before you do anything else - fully charge each battery out of the truck and test them to ensure they are good.

How did you try to bypass the LBCD? If you hook the 24v batt/load cables together one one stud, and the 12v batt/load cables together on one stud and disconnect it's cannon plug that should eliminate it and everything should work correctly - voltage gauge should read about 0.3v higher without the LBCD in play.

Red light means over-voltage cut-out. I had a similar intermittent issue like that and it turned out to be a cold solder joint on the ground lead for the LBCD inside it's control harness cannon plug.

Review my thread on a similar issue.

2008 A1R with 260a charging questions

Currently has a brand new N3221 voltage regulator (2012 vintage I believe - was new in the box with papers). The truck had a 2013 regulator when I picked it up in Houston. It died about 100 miles from Portland - 2600 miles into the trip back. I put in the brand new spare and drove the last 100...

www.steelsoldiers.com

OK so a little update... I ran all the 12Volt terminals together and all the 24 volt terminals together. No change. I looked for a cannon connector but was not able to see one. Does that mean it is a polarity protection device and not an LBCD? I ran a wire from the battery to the to excitor. Well the voltage regulator was not happy about that. Instead of the LED flashing orange/green it was flashing red for about 15 seconds and then quit. I have noticed that if it flashes orange/green my volts stay up, if it goes red, that is when they drop out. First question is where would the cannon connector be if it has one? Next question, is there a difference between a polarity protection device and a LBCD?

 

[Rick_bagby]

that rules out an Acert being swapped in it, so unless it is an odd animal (and it happens) its a 3116 (aka..... engine swapped in later up the road by military... usually have black valve cover) so you should have giant sticker on top of yellow valve cover.

//uploads.tapatalk-cdn.com/20171111/ea205030fbfe9bb61f274f0ed9b6447c.jpg

After climbing up in engine, it is indeed a 3116. Big white label on the valve cover.

 

[Rick_bagby]

Run a new ground cable from the batts negative to a sanded spot on the main frame rail. I would then run a temporary wire from the battery positive to the front terminal on the regulator. See if your voltage still drops out.

OK so a little update... I ran all the 12Volt terminals together and all the 24 volt terminals together. No change. I looked for a cannon connector but was not able to see one. Does that mean it is a polarity protection device and not an LBCD? I ran a wire from the battery to the to excitor. Well the voltage regulator was not happy about that. Instead of the LED flashing orange/green it was flashing red for about 15 seconds and then quit. I have noticed that if it flashes orange/green my volts stay up, if it goes red, that is when they drop out. First question is where would the cannon connector be if it has one? Next question, is there a difference between a polarity protection device and a LBCD?

 

[Rick_bagby]

Bad batteries can cause a voltage spike and shut the alt down but you would still have battery voltage at the dash gauge. Does the truck have a small box to the right of the battery box? There is a low voltage cutoff relay in there. I would also check all the grounds. The main ground cable goes thru a current shunt up by the lbcd. I would remove the shunt and make a good ground connection.

I will be taking the shunt out of the equation next. and probably replacing grounding straps to eliminate that as a possible problem. There are a lot of those straps.

 

[Ronmar]

So have you run the volt meter tests at battery and power panel I described a few posts back? You seem to be just trying stuff without really identifying what is happening. I call this troubleshooting in a Vacuum,

measure 12 and 24 to chassis ground at the batteries. With charged batts should be ~12.8 and 25.6V

measure panel 12 and 24 to the ground test point on the left side of the power panel. Should be 1/2 volt less than what you saw at the batteries.

Turn on the ignition switch and measure again. You should have the same 1/2 volt drop on both 12 and 24v between batts and panel. You must have these conditions before you can proceed… more than 1/2v drop between batts and power panel when loaded indicates a bad connection. This is a common problem on the polarity box connections as they are out in the weather. I have had one myself… you can increase the 12v load by turning on the headlights, the 24v by turning on the heater blower for these tests…

If you have the above conditions, while measuring 12V at the panel test points, start the truck while watching the 12volts. It should dip while cranking but return to 13.6 when the engine starts and the alt comes online.

if your troubleshooting in a vacuum that means I am troubleshooting in a vacuum. Collect me some data so I can help you…

 

[Rick_bagby]

So have you run the volt meter tests at battery and power panel I described a few posts back? You seem to be just trying stuff without really identifying what is happening. I call this troubleshooting in a Vacuum,

measure 12 and 24 to chassis ground at the batteries. With charged batts should be ~12.8 and 25.6V

measure panel 12 and 24 to the ground test point on the left side of the power panel. Should be 1/2 volt less than what you saw at the batteries.

Turn on the ignition switch and measure again. You should have the same 1/2 volt drop on both 12 and 24v between batts and panel. You must have these conditions before you can proceed… more than 1/2v drop between batts and power panel when loaded indicates a bad connection. This is a common problem on the polarity box connections as they are out in the weather. I have had one myself… you can increase the 12v load by turning on the headlights, the 24v by turning on the heater blower for these tests…

If you have the above conditions, while measuring 12V at the panel test points, start the truck while watching the 12volts. It should dip while cranking but return to 13.6 when the engine starts and the alt comes online.

if your troubleshooting in a vacuum that means I am troubleshooting in a vacuum. Collect me some data so I can help you…

I am sorry Yes I did get that information. At batteries I have 12.7 and 25.4. at the PCP I have 12.3 and 25.0 It is just me so starting and measuring are proving difficult at the moment for the other readings.

 

[coachgeo]

... It is just me so starting and measuring are proving difficult at the moment for the other readings.

been there. set up meter and phone in a way that phone will record it. You likely will need to grab some vice grips, clips or the likes to hold probes of meter in place. Then use phone to record the readings when you try to start truck or put load on them like head lights ....... yell somthing for phone mic to pic up so you have a mark in the video of when you do things you want to be able to compare with meter.

granted simpler way is something like below and move the meter to where you can read it. They have them at Autozone and the likes

https://www.amazon.com/Lang-Tools-1129-Retractable-Test/dp/B000KIVOU2

 

[Ronmar]

Well the loaded/switch on test is the most important. Voltage is never considered good unless tested under load... you should be able to do that by yourself, i do it by myself, hook up the meter and flip the switch...

 

[Rick_bagby]

I am working on a 1995 Stewart Stevenson M1078 A. I am having an issue with the charging system. CB77 is good as is K11 relay. However after about 30 seconds my volts gage drops to 0. I pull either CB77 or K11 and reinstall it, the volts go up to about 27-28 for about 15 seconds, and then drop off to zero again. I have cleaned the terminals on the LBCD, Battery cables are good, and the excitor is still having issues. The red light comes on the voltage regulator, and that is when the volts drop off. Can anyone give me some insight as to where the problem may be? I have tried to by pas the LBCD and unit will not even power up when I hit the green button on the dashboard. This tells me that the LBCD is doing its job. I tried going from battery to excitor. That does not work and it powers up the CTIS directly. I am trying to get this going for a fire department to use so any suggestions would be appreciated.

Update: so after going through the drawings and finding no reason why my voltage should be dropping out (a major clue in itself) and listening to many of you on here, I am trusting the readings and going with a bad voltage regulator. Finding no discontinuity in the wiring, voltage where and what it should be all the way back to the alternator and regulator, the HVCO in the regulator is shutting off when the voltage is correct. Shutting offf the 14 volt side with only 13.2 volts and the 28 volts at 26.7 (both LED’s are red and shuts down alternator). Far below the set point. New one on order. Thank you for all your help in getting me to focus, run the numbers, and trust the answers. Y’all are awesome.

 

[Rick_bagby]

Run a new ground cable from the batts negative to a sanded spot on the main frame rail. I would then run a temporary wire from the battery positive to the front terminal on the regulator. See if your voltage still drops out.

spot on with the grounding. Somewhere along the way prior to me getting it, someone removed a few of the ground straps. Including the ones from the (-) battery to the GND of the alternator and from that same ground point to the frame. Settled all the numbers right out so I could find the cause. Thank you.