M923A2 Electrical Issues - No STart - No Power

[JM923A2]

I have searched the forums and found plenty of information about certain electrical parts, the issue is mine went out all at once. I just received my M923A2 from Ft. Riley of which ran when slave jumped by the seller to load onto the flat bed. The truck was shipped directly from Ft. Riley to Colorado with only a fuel stop. When it arrived it had no batteries so we attempted to jump the truck with his trucks 24v System @ up to 4k amps. He said he hopped into the driver side and toggled the battery on. Then moved the toggle to run and let it sit everything was buzzing etc... when he went to start it by turning it further all electrical shutdown and no gauges worked. We attempted to jump the vehicle from the starter and it would spin but not engage the flywheel. I then added batteries and still no indication that electrical is working. I am thinking it is either the Electronic Control Unit, or the Protective Control Box.

Would the entire system refuse to start if either of these units stopped working?

 

[Swamp Donkey]

When you say no electrical, does that include exterior lights? Does the blower motor for the heater work on low? Neither of those two things are related to the PCB. If neither work, I'd look somewhere else first besides the PCB. If both work, I'd give the PCB a couple smacks with a mallet with the battery switch in the ON position and see if your gauges light up.

The PCB can cause a no start situation, among other things, but verify you actually have no electrical before you point the finger at it.

 

[JM923A2]

When you say no electrical, does that include exterior lights? Does the blower motor for the heater work on low? Neither of those two things are related to the PCB. If neither work, I'd look somewhere else first besides the PCB. If both work, I'd give the PCB a couple smacks with a mallet with the battery switch in the ON position and see if your gauges light up.

The PCB can cause a no start situation, among other things, but verify you actually have no electrical before you point the finger at it.

Thank You for the reply,
I did not notice any lights or the blower working indicating that there was 12v running in the system. I will double check later to validate this as it was late and I was tired.

 

[Suprman]

There is no electronic control unit. The pcb is just 2 relays. You need to make sure the wiring is connected properly. The big positive cable from the battery box goes right to the starter as does the ground. If you tried to apply power to the starter without engaging the throw out solenoid then it will just spin and not engage. Do you have a multimeter? Everything is 24v on that truck except for the heater blower low speed.

 

[JM923A2]

There is no electronic control unit. The pcb is just 2 relays. You need to make sure the wiring is connected properly. The big positive cable from the battery box goes right to the starter as does the ground. If you tried to apply power to the starter without engaging the throw out solenoid then it will just spin and not engage. Do you have a multimeter? Everything is 24v on that truck except for the heater blower low speed.

I checked with a multimeter 24v to the system. No lights on dash or headlights work. Check the battery area for lose wires found 2 frayed. Patched and same issue. The mallet solution also didn't work. I am stumped, all grounds and cabling looks good. The only thing is the pcb that I cannot check is there a way to test it?

 

[Suprman]

24v positive and negative at the starter? Did you make sure the power cables didn't end up reversed at the batteries?

 

[JM923A2]

24v positive and negative at the starter? Did you make sure the power cables didn't end up reversed at the batteries?

I checked and they looked good. The one with a red boot on both sides is in the correct spot it even has the epoxy still on the starter. Either it's a ground that is bad, which I looked for and found nothing. It started at Ft. Riley just fine so something had to change on transport. The weird part is that the starter has 24v have two extra batteries so I am thinking of trying a starter start. Just don't know if that's wise with the batteries inside connected. when the semi driver tried jumping it the whole system turned on until it was pressed to start. It then cut out, with the small gage wires frayed inside the battery box I wonder if it wasn't grounded and it fried the PCB. That may also explain the gear not engaging the transmission to start it. Any thoughts?

 

[Suprman]

I am still not confident things are properly connected. Post a good pic of your battery box and read the TM's. The pcb is just 2 mechanical relays.

 

[The HUlk]

I am still not confident things are properly connected. Post a good pic of your battery box and read the TM's. The pcb is just 2 mechanical relays.

Yep, sounds like when the 24V jump occurred, perhaps there may have been some damage done. A misconnection somewhere would be the likely cause.

 

[Shark Bait]

One of my M931A2's one day wouldn't do anything. I thought perhaps something was left on and drained the batteries. I charged them but they weren't dead. Upon further investigation it turns out the battery disconnect switch on the dash seems to be bad. You can wiggle it back and forth a few times and position it in a certain spot and gauges and lights will come on and truck will start. I haven't pulled it apart to diagnose it yet to see exactly the issue with the switch. I will but may be a few weeks.

Dave

 

[The HUlk]

I checked and they looked good. The one with a red boot on both sides is in the correct spot it even has the epoxy still on the starter. Either it's a ground that is bad, which I looked for and found nothing. It started at Ft. Riley just fine so something had to change on transport. The weird part is that the starter has 24v have two extra batteries so I am thinking of trying a starter start. Just don't know if that's wise with the batteries inside connected. when the semi driver tried jumping it the whole system turned on until it was pressed to start. It then cut out, with the small gage wires frayed inside the battery box I wonder if it wasn't grounded and it fried the PCB. That may also explain the gear not engaging the transmission to start it. Any thoughts?

When you turn the 24V electric switch on the dash to the up(on) position, does the voltage gage move? If so is it in the red,yellow, or green range?

 

[JM923A2]

When you turn the 24V electric switch on the dash to the up(on) position, does the voltage gage move? If so is it in the red,yellow, or green range?

No nothing moves with the battery switch on the dash. What I did do to check if it is the PCB is remove the primary cable and bypass it using wires from B-C and C-D. The truck fired up after a little crank to get fuel to the cylinders no longer than 5 seconds. Inside once on, the battery switch did nothing, however all the instruments worked battery voltage was fluctuating between green and above green until the gas pedal was pressed. Once pressed the power become steady in the green. I think both switches may have been damaged by the surge that fried the PCB. Either way I am getting another one and trying it just to verify. As for the switches I am thinking about doing a 2 key system one for the batteries and one for starting.

 

[JM923A2]

Update, I replaced the PCB and still the same issue. The system jumps when I bypass the PCB. Once it's connected nothing turns on. Any thoughts? I know it's a good PCB.

 

[The HUlk]

Update, I replaced the PCB and still the same issue. The system jumps when I bypass the PCB. Once it's connected nothing turns on. Any thoughts? I know it's a good PCB.

The fact that your battery switch seems to do nothing is my thought. You can confirm it is working, and providing power to the PCB by...

connect everything as it should be.

measure at the battery switch:

terminal A(wire81A) to GND should always read 24VDC
terminal B(wire459) to GND should read 0VDC in the off position, and 24VDC in the on position.

measure at the PCB:

terminal A(wire459) to GND should read 24VDC when the battery switch is on.

 

[therooster2001]

Did you get it fixed? I'm up north, but sometimes two brains are better than one. Willing to check it out with you...

 

[The HUlk]

Did you get it fixed?

Kinda makes yah worry eh? Hope he's okay. And curious as to if the problem was solved and what the root cause was?

 

[MtnSnow]

The OP hasn't been back onsite since the 23rd posting date.

 

[The HUlk]

Figured it out and didn't bother to pass along what was learned? Hope he's just been busy and things worked out.

 

[Finallygotone]

Help please, I have a M923A2, I have not power to anything when I flip the main switch, no lights, It has a 48 volt system so I removed all the cables and charge all the batteries, has never fail to start and start quick, sounds like the switch does not have the snap sound that is used to have, just prior to this I left the light switch on with the dash lights and the switch to the left of it, maybe that caused this switch to over heat if that is possible, your fellow have faced this before I am sure and I won't leave a switch on again, thanks all for the help in advanced, Joe

 

[The HUlk]

Is it possible the cables were reconnected incorrectly?