Won an M1083A1 - 1900 mile recovery trip soon! (ND to CA)

Eaglhawk

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My surplus yard is 7 miles off I-80 by Grantsville utah, just 40 minutes outside Salt lake city on the way to Wendover NV. If you have problems in the area let me know and I will help any way I can.
 

dxhend2

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We got to the Load Battery Control Device and it's reading 24v on the load and battery terminals 24v side), checked the 12v terminals, reading 12v to ground on both load and battery side. From what I understand, sounds like its working properly.
We might try Superman's suggestion of running a new wire from 24v terminal on the fuel pump over to the 24v terminal of the voltage regulator, but I don't have a good understanding of how that might solve this. Still checking...

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Jbulach

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We got to the Load Battery Control Device and it's reading 24v on the load and battery terminals 24v side), checked the 12v terminals, reading 12v to ground on both load and battery side. From what I understand, sounds like its working properly.
We might try Superman's suggestion of running a new wire from 24v terminal on the fuel pump over to the 24v terminal of the voltage regulator, but I don't have a good understanding of how that might solve this. Still checking...

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Remember, just because your meter reads good voltage, doesn’t always mean you have a good current carrying path. When you try to apply the load, the correct voltage may drop off or disappear, down stream of your problem.
 

NDT

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If the LBCD checks out, next downstream is the power distribution panel, which was soldered with RoHS solder and is subject to intermittent connections.
 

dxhend2

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Thanks, NDT. We're in the PDP now, that has to be the common point. The ignition power and start switches on the alternator have no effect, same as their counterparts on the drivers dash - looks like they all go into the PDP. We've swapped around all the 24v relays, even bought a few new ones, no effect. Could be some solder connections as you mention; will dive deeper into the PDP. Are the circuit boards behind the relay boxes? Also, the "neutral start" relay is 10 degrees warmer, all others ambient. We've swapped that one with several others, they all warm up in that slot. A clue?

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Jbulach

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Did you try bypassing the pdp as suggested earlier? Just unbolt the output cable and stack it on the input.
 

Suprman

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Try disconnecting the military twist plug from the lbcd and see if it will power up. The number one reason an A1 truck wont start is batteries and/or battery connections. There is a big shared ground at the starter also. Even if you are reading 24 volts does not mean the batts are good. Did the batts come with the truck? In warm climate you can get away with 2 batts as long as they are newer. Napa has 6tls sometimes. Until you have 100 percent verified good batts you cant troubleshoot further. Low voltage and the battery disconnect contactor wont activate. I have seen this same thing several times.
 

dxhend2

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Thanks, Superman. We have four new batteries, type 24H (recommended in another thread), 750 CCA each. We're seeing 12.4v on all batteries. Will try disconnecting the control cable to the LBCD. In the meantime we have the PDP mostly disassembled, looking for any bad solder connections as suggested, also.

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Suprman

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Check the ground at the starter and all the batt connections. It sounds like the master relay isnt powering on. Its in a box to the right of the battery box. There is also a manual cutoff switch that can be accessed under the box.
 

dxhend2

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Well, we've shutdown for the night after a full day of troubleshooting. Luckily we're at a stop in Jamestown, ND with hotels and food right here, so we're in good shape and good spirits. Thanks for all the posts, texts and calls today - very helpful and greatly appreciated! Lots of locals have stopped and offered to help, but no one has ever seen anything like this. Each time we stop to explain what the sysmptoms are, what the different components are, what we've tried, etc., it just reinforces our understanding of how this truck works (I think that's just the natural process of how we all learn about MVs).

Today we focused on the Power Distribution Panel (PDP) - the mess of relays and circuit breakers on the right side of the dash. We were thinking that was the common point between the dash controls (master power switch and start button), and their corresponding swiches just behind the alternator (apparently a feature of the A1's that allows remote starting of the engine when the cab is raised) - looks like both go through the PDP to control relays that then control the starter solenoid relay among other things. Swapped out all the relays, and replaced three with new ones - no effect. Dash will not light up at all, still have 12v power to all lights. Verified that the starter has a good ground, also.

I've included some photos below of the A1 PDP since there's not much info out there on these. One oddity we can't explain is in the last photo - the relay/breaker box on the far right -the power connector coming in from the bottom right (circled in red) is reading +4v, other relay boxes were getting 12v inputs.

Based on many suggestions that came in through this thread today, we've worked up a pretty good sequence of testing for tomorrow:
- Verify battery grounds
- Verify master relay operation (in box to the right of battery box; there is a rotary switch on the bottom of this one). Will test both from dash and from remote switches by alternator.
- Remove control cable from the Load Battery Control Device (LBCD - reverse polarity ddevice) and attempt to start (if success, get in and go!)
- Safe the LBCD (disconnect batteries, discharge capacitors via ignition switch)
- Verify all battery voltages
- Bypass LBCD by stacking the leads on common posts for each side (12v -> 12v, 24v -> 24v)
- Reconnect batteries, attempt to start #2

If that doesn't work, we're looking at ideas of what else to bypass to get power to the dash and power to the starter. If you have any ideas on the next areas of focus, please post here (I'm also up on cell/text at 619-886-2531).

02_Cabin_Battery_Disconnect.jpg02_Master_Switch.jpg03_12v_Lights.jpg04_Remote_Start.jpg05_insidePDP.jpg06_PDP_Closed.jpg07_PDP_Open.jpg08_PDP_Closeup.jpg09_PDP_Analyzed.jpg
 

Suprman

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The lbcd is basically a diode array that prevents cab electronics damage if someone connected the batteries reverse by accident. It also aids in battery charge regulation. They do go bad and will cause an improper charging situation. Let me know if the master relay is energizing with the power cut switch. The quad block power panel is pretty reliable does not suffer from bad solder joints like the earlier printed board type. If you can find a pair of 12v chargers try separating the battery banks and charging. All of the relays are 12v if someone shows up to give you a slave port jump and the batts are weak you don’t always get the 12v you need from a 24v jump. You can also go to the starter with a clip lead onto the inner solenoid terminal to positive if you want to crank the motor.
 

dxhend2

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Suprman, thanks for those suggestions. We verified the master power relay is working. Your suggestions on batteries got us thinking on that route. We have a fifth 12v battery that we carefully added in parallel to the 12v bank, no luck, then moved it parallel with the other bank (12-24v range), no luck there either. We also tried shorting across the starter solenoid relay and got a good, healthy crank of the engine, but would not start. Pressed manual primer to ensure fuel was up and cranked again, no start. But, that tells us that the starter side of things is good. Removed the control cable to the LBCD, no effect. Right now we're bypassing the LBCD (stacking 12v and 24v leads on separate terminals). After that we could try charging all the batteries, but from the two cranks, sounded like there was plenty of power in them (but, with electronics, it could be a whole other story). Will post again after LBCD bypass; after that, back to drawing board.

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Suprman

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Its an electronic engine and will not start if no power to engine computer. Pull up the power panel there are 2 relays under there make sure all connections are tight. In the engine bay sometimes there is a filter that the engine computer power goes thru. Have seen that fail and trip a breaker. Take a mulitmeter on voltage and go from the ground on the power panel to the negative terminal on your batteries. If it shows voltage then you have a ground issue somewhere.
 

Suprman

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Maybe its something stupid like your dash power switch went bad. Seen that before. Alot of the switches are the same the legend just pops out. You can try swapping switches.
 

dxhend2

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We can try that next. The remote ignition and start switches by the alternator don't work either, so we were thinking it was something upstream and common to both.

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