Can't get power to come on in Renogy 40 amp DC to DC charger

Hooked up my Renogy 40 amp DC to DC charger today just like this diagram. Grounding wire ran from the DC to DC charger to the chassis, then the house battery on the load side of my shunt. Found am ignition fuse spliced into it with an "add a fuse" and connected that to the D+ to power on the charger when the ignition was started. I got no power on the DC to DC charger. Checked the voltage on the D+ wire with the engine running, it looked good (13.2 volts) Besides a faulty charger, what could be keeping this from working?! The starter battery should already be grounded to the chassis, right? That is the common ground for the charger and house batteries. Thanks.

 

That charger should be wired to the battery I believe. If it needs to be ignition switched, then a relay installed between the battery and charger, triggered by the ignition power source you tapped into.

 

Technically, it IS wired to the battery because of the common ground. The hot wire runs directly from the starter battery to the charger, but the ground is just chassis grounded. Makes me think the starter battery is not grounded to the chassis, but that just seems crazy that Toyota would do that. Isn't the chassis the common ground for nearly EVERYTHING?!

 

The starter battery is ground wired to the body and the engine block.

 

Does "body" include the chassis? Please forgive my ignorance, but this is my first experience with this.

 

Problem solved! Either I was just dead wrong in my understanding, or the starter battery is NOT grounded to the chassis! All I did to fix it was the also run a wire from BATT - to Charger -. Fired up the truck and the charger lit up for the first time! Reads a full 40 amps at the shunts that are in the battery box in the bed of the truck.

Some of the diagrams I saw are just wrong. Water under the bridge though. It's installed and working, so let them be wrong! Lol

Thank you for the response, Knab. I'm most obliged.