No start (fixed) - Charging System light on

[SpaceGhost]

Hi all,

I am currently stuck mid-trip and my M1078A1 will not start. I went through this earlier with a WTECIII issue, but resolved it. Now the Charging System light is illuminated and the vehicle will not start. In the 24 hours before this happened, I was intermittently losing 12v power to the dash and the exterior lights would go off if the engine was not running with the main power switch on. With the engine running everything was working fine. Battery voltage (measured on the batteries) is 12.8 x2 and 13.1 x2, however battery voltage at the PDP reads ~6 volts for the 12 volt bolt and ~16 volts for the 24 volt bolt. There is no power to the 12v and 24v ignition bolts on the PDP with the main ignition switch on.

Any help would be appreciated!!

Thanks,
Bryan

 

[TheDrashStash]

Check the anti polarity reversal box, it's under the spare tire carrier. follow the battery cables from the battery box and it goes there before going to the rest of the truck

 

[TheDrashStash]

To be more specific, I believe it's under the air/hydraulic power pack.

 

[Ronmar]

Sounds like the main battery disconnect relays are not energizing. They are controlled by the LBCD/polarity box that thedrashstash mentioned. On the A1/A1R It senses alternator load From the regulator and will disconnect the batteries if the alt is overloaded(one way to deal with a small alt and a grossly oversized battery) While allowing the alt to continue to power the truck. The LBCD also controlls that charging system light in the dash.

The power path is batteries, manual disconnect, disconnect relays, polarity portion of LBCD, and 12 and 24V testpoints in the dash. Then on to the ignition relays. The alternator injects it’s power between the LBCD/polarity box and the disconnect relays. The manual disconnect and the disconnect relays are all located back at the batteries so should be able to easily step along from the batteries with a voltmeter and the main switch on, to see where the power stops. I would also make sure the external battery disconnect sw is not in the wrong position…

if the disconnect relays are not energizing, you should be able to bypass them fairly easilly to get you back on the road. I would also look closely that the batts are OK and that the running voltage at the batts floats up to 14.1/28.2v…

 

[SpaceGhost]

Sounds like the main battery disconnect relays are not energizing. They are controlled by the LBCD/polarity box that thedrashstash mentioned. On the A1/A1R It senses alternator load From the regulator and will disconnect the batteries if the alt is overloaded(one way to deal with a small alt and a grossly oversized battery) While allowing the alt to continue to power the truck. The LBCD also controlls that charging system light in the dash.

The power path is batteries, manual disconnect, disconnect relays, polarity portion of LBCD, and 12 and 24V testpoints in the dash. Then on to the ignition relays. The alternator injects it’s power between the LBCD/polarity box and the disconnect relays. The manual disconnect and the disconnect relays are all located back at the batteries so should be able to easily step along from the batteries with a voltmeter and the main switch on, to see where the power stops. I would also make sure the external battery disconnect sw is not in the wrong position…

if the disconnect relays are not energizing, you should be able to bypass them fairly easilly to get you back on the road. I would also look closely that the batts are OK and that the running voltage at the batts floats up to 14.1/28.2v…

Yesterday, I measured 13.1 volts from the disconnect relays. The missing piece was the LBCD, which I wasn't even aware of until you and DrashStash pointed it out. It seems like that is the missing link. I am hoping there is a way to bypass that if we can determine that is indeed the problem. It looks like you have to move the spare tire out of the way to get to that, is that correct?

Assuming we can get it running again, I will check the running voltage at the disconnect relays and on the PDP to make sure we have 14.1/28.2v.

Thank you so much! Love this truck, but it can be challenging at times!

 

[TheDrashStash]

Yesterday, I measured 13.1 volts from the disconnect relays. The missing piece was the LBCD, which I wasn't even aware of until you and DrashStash pointed it out. It seems like that is the missing link. I am hoping there is a way to bypass that if we can determine that is indeed the problem. It looks like you have to move the spare tire out of the way to get to that, is that correct?

Assuming we can get it running again, I will check the running voltage at the disconnect relays and on the PDP to make sure we have 14.1/28.2v.

Thank you so much! Love this truck, but it can be challenging at times!

Removing the spare tire, or at least lowering it gives you decent access. I think I had to remove a part of the air intake too. I had one go out on a truck and you can test it easily. It's been a while but there are 4 posts, 24v going in and out, and 12v in and out. test with a multimeter

 

[TheDrashStash]

This is what it looks like

 

[ldmack3]

Where are you stuck?

 

[SpaceGhost]

Where are you stuck?

We are in Ogden, Utah. After a bit of sleep and a good breakfast we came back out with fresh eyes, and I think we found the problem. The bolt attaching all the wires to the starter came off.

Anyone happen to know what size that is?

 

[Ronmar]

Yep, thats your main ground point, that will cause issues… The large wire hanging free is the lead back to battery negative. From what I understand of the LBCD, if it is working correctly, it should allow battery connection/close the disconnect relays when energized. But with that large lead disconnected at the starter nothing is getting energized when the lead came off, it probably caused the alt to do weird things which the LBCD saw and it engaged the charge light on the dash, as you most definitely had a charging issue…

 

[simp5782]

Metric M12 to M14 size range

 

[SpaceGhost]

Thank you everyone! This is such a great community and resource.

That was the issue, and she fired right up after replacing it. It was either 12mm 1.5 thread or 1/2"-20. Those two looked the same and I couldn't tell them apart once I got back to the truck with them.

Back on the road!

Cheers,
Bryan

 

[coachgeo]

... It was either 12mm 1.5 thread or 1/2"-20. Those two looked the same and I couldn't tell them apart once I got back to the truck with them.

Back on the road!

Cheers,
Bryan

congrats.

when life allows..... stop by tsc or similar to find out what nut you didnt use so you can report back on what nut you did use?

 

[simp5782]

Put silicone on your finger and wipe it on the threads and nut. You find this on alot of the trucks