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I'm adding a fuse block (pdm60) and need to find a trigger wire that I can tap in to near the front driver seat somewhere that's only on when the key's on. Any suggestions? Any in the battery compartment?
 

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Trigger wire

An easy ignition source to tap off, would/could be the accessory power plug on the center console just right of the switch panel. The wire is easily accessed by removing the lower center panel, attached to the lower cup holders. 1:pulling upward and removing the lower cup holder reveals 2 screws (remove). 3:Then remove the two upper screws behind little rectangular clip panels. 4: Grasp the lower center panel evenly from each side and firmly pull it off. There are about 6 clips that will release and pop off. Look at where the 12vdc accessory plug is, and you will see the connector and wires (hanging just below)that can be spliced or tapped into. My opinion this is a great area of space to mount a relay, access ground from frame mount bolts or hide wiring.:)
 

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... and there's lots of room behind the easily removable cupholder to put relays, fuses, etc.

I tapped off the lighter plug and dropped a wire to the bottom where I plug in my GPS adapter. Easy to pull the cupholder to access if I need to.

Ed
 

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Large blue wire at the BCM just behind the driver panel under the steering column.
So Im also trying to add an ignition on hot wire to a battery isolator. I have a 2019 promaster 2500 without any auxiliary switches. Im looking at the BCM but don't see a large blue wire. I also took off the center console and found the wire under the cigaret lighter but that wire goes hot when the key is partly turned before the ignition turns on. Any other ideas?
 

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deleted... output signal present w/o engine running​
((F942) Fused Ignition Run/Switch Output circuit at the PCM C1 harness connector (cavity 54) - danger will robinson)
 

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So Im also trying to add an ignition on hot wire to a battery isolator. I have a 2019 promaster 2500 without any auxiliary switches. Im looking at the BCM but don't see a large blue wire. I also took off the center console and found the wire under the cigaret lighter but that wire goes hot when the key is partly turned before the ignition turns on. Any other ideas?
You can also check the upfitter connections behind the base of the passenger-side B-pillar cover. I think one or more of them may be ignition (engine running) hot. This website has the details:
https://www.ramtrucks.com/ram-commercial/body-builders-guide.html
Also double check your isolator specs. Some, including my Bluesea ML-ACR, have an option that calls for crank-only hot. That version doesn't exist in the upfitter connections. You have to tap the starter circuit for that. That particular option is just for protecting sensitive electronics from starter spikes. None of my electronics are that sensitive, so I skipped it. That likely just applies to things like ambulances, surveillance vans, etc.
 

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So Im also trying to add an ignition on hot wire to a battery isolator. I have a 2019 promaster 2500 without any auxiliary switches. Im looking at the BCM but don't see a large blue wire. I also took off the center console and found the wire under the cigaret lighter but that wire goes hot when the key is partly turned before the ignition turns on. Any other ideas?
To trigger the isolator, I would still recommend the wire in the center console. Why?

1) I'd stay as far away from the BCM-connected wires as possible...if something ever goes wrong, the warranty question will be "what this wire connected to the BCM?"

2) the center console wire is easy, protected by a 15 or 20A fuse, and if it is on when the key is in the pre-run position, it won't do any harm, it just will connect the two batteries - IF the voltage on the van battery is high enough.

3) My Battery Doctor isolator has been connected there for 4+ years with no issues...
 
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