This has me somewhat stumped. I've got an ARB base rack on my 300, and was trying to set up a chassis negative on the roof so I don't have to run two wires. Found that the mounting bolts for the base rack mount kit presented zero ohms in a continuity test to a random other chassis point - I used the middle row seatbelt anchor point in this case.
So I pulled said bolt out, cleaned it up with a wire brush for good measure and inserted a copper ring terminal crimped to a short length of 8AWG terminated in a 50a anderson. Ran my positive down the side of the tailgate and in through a grommet found behind the tail light cluster. I picked up the negative on the same point I tested and is used by my aux batteries in the back, the seatbelt anchor, and terminated again with 50a anderson. So between the two andersons, in the back of the vehicle and the roof, positive is wired by a single 5m run of 9AWG double sheathed solar cable (UV stable as I live in Australia), and negative from anderson to chassis at seatbelt mount via 0.5m of 8 AWG, then from roof rack mount bolt to anderson again via 0.5m of 8 AWG. Continuity across both conductors shows zero ohms.
Hooked up to battery bank and I see a PD of 13.71v on the roof, exactly the same as I get on the battery direct, BUT - there's no current. Well practically anyway. It can light a small bulb, but any more significant loads do nothing. I used my 200lpm compressor to test, and got zip.
So I depinned the negative at both ends and ran a cable between them, still using my newly installed 9AWG for the positive and the compressor runs at full power.
How is this possible? Welcome thoughts to troubleshoot.
Cheers.
-edit- I've just tested both half-metre negative cables in isolation and both work fine.
So I pulled said bolt out, cleaned it up with a wire brush for good measure and inserted a copper ring terminal crimped to a short length of 8AWG terminated in a 50a anderson. Ran my positive down the side of the tailgate and in through a grommet found behind the tail light cluster. I picked up the negative on the same point I tested and is used by my aux batteries in the back, the seatbelt anchor, and terminated again with 50a anderson. So between the two andersons, in the back of the vehicle and the roof, positive is wired by a single 5m run of 9AWG double sheathed solar cable (UV stable as I live in Australia), and negative from anderson to chassis at seatbelt mount via 0.5m of 8 AWG, then from roof rack mount bolt to anderson again via 0.5m of 8 AWG. Continuity across both conductors shows zero ohms.
Hooked up to battery bank and I see a PD of 13.71v on the roof, exactly the same as I get on the battery direct, BUT - there's no current. Well practically anyway. It can light a small bulb, but any more significant loads do nothing. I used my 200lpm compressor to test, and got zip.
So I depinned the negative at both ends and ran a cable between them, still using my newly installed 9AWG for the positive and the compressor runs at full power.
How is this possible? Welcome thoughts to troubleshoot.
Cheers.
-edit- I've just tested both half-metre negative cables in isolation and both work fine.
Last edited:
