No start, no cab power issue

[Engineman2018]

Good morning all,

Truck is a 2019 petervilt 389 with an X15.

I have an interesting issue. A truck i work on broke down at the local coop. Driver stated "truck wont start, started many times previously this morning," boss suspected a starter. Got to the coop and tested battery voltage and connectors, voltage at starter and voltage while cranking. All wired and cables checked out good. I noted that all voltages were good but there was no voltage from the exciter wire. I turned my attention to the cab and fuses and immediately noticed there was zero cab power. No cab lights, no dash lights, no headlights, clearance lights, brake lights, turn signals and hazards. no radio or CB chatter. Wipers worked on high but no other settings, washer pump didnt work, no light switches worked. While keyed on, the ECM did wake up and THE ABS module went through start up. I checked all fuses, powers and grounds and relays with no discrepancies found. With the coop backing up, I decided I'd see if the truck would start. I keyed on and jumped the starter and moved the truck out of the line and to a better area to work on. I inspected a few more things before we got rained out and moved the truck to the shop. I removed the grounds from the battery while we discussed a plan. When I reconnected the grounds, the issue was no longer present. All cab power returned and everything worked as should. I cant wrap my head around it and cant replicate the issue. Any insight would be greatly appreciated. Please let me know if you have questions or need clarification and ill get it done.

[Rawze]

Paccar chassis controllers (Pete and KW) are known for the control modules occasionally getting flaked out, causing someone to disconnect the batteries for 30 mins to hard reset it.

== ghosts like ...

== guage lights acting up or not illuminating then headlights are on/off, etc.

== no-start with nothing on or responsive in the dash (like you described).


== Interference like ... A nearby (or internal) Big honkin' illegal CB radio, bad grounds, nearby radio station, excessive alternator noise from alternator diodes getting weak, etc. .. An after-garbage e-log device that is not friendly with the J1939,.. you name it.

== Another very common cause is old fuses (several years old) that have tarnished/discolored blades, even though they are still electrically still good. == Any time there are unexplained ghosts in an older truck,.. one of the first things to do is replace ALL the fuses in the panel with new ones if they are more than a few years old. Also ensure no one has put a bigger fuse in than it calls for.

[Engineman2018]

Thank you for your response Rawze. I referenced one of your previous posts regarding the unreliablility of the CECUs to my boss, emphasizing how the issue disappeared when batteries were reconnected. I am currently cutting wires to under glow lights that were installed by a previous driver to see if thats been an issue. I will run through the fuses and replace all of them as well seeing as its a cheap and quick thing to do.

Another thing I noticed, when keyed on engine off, if the blower motor was turned on high, the amp gage would read a 25±10 amp draw on system with the red indicator light illuminated.