Adding voltmeter - Need ground wire. UPDATE

I’m adding the voltmeter to the panel where the switches for slide/awning/lights are located. There are several 12 volt “hot” wires inside the panel, but I’ve yet to find a ground connection. 

I wired industrial equipment for 35 years, ranging from millivolts to 600 VAC, but I’ve never seen wire colors such as this. The “hot” wire to the awning is green!!!  Green is always ground on 120VAC systems. And black is usually ground on 12VDC systems. Some of the 2 conductor wires even have power on both conductors!  It looks like each wire was run by a different person. 

Does anyone know if there even is a ground in the panel?

Thanks,

John

It took me a while, but I finally got it put in. It’s mounted near the radio, but the radio ground wire looked too small to carry any extra current. Looks like maybe 20-22 gauge. 

I found a YouTube video that explains the converter wiring, both 120 AC and 12 VDC. I pulled the converter from the wall and there is a buss bar for all the DC grounds, behind the converter, mounted to the floor!?  The AC neutral and ground buss are accessible with just taking the cover off the converter. The hardest part was pulling the wire, up through the wall, from the converter at floor level, to the radio panel close to the ceiling

I connected the hot lead to a wire coming out of the converter. I’ll try to get pictures tomorrow.  I always put one of these meters/chargers on all my motorcycles, for an accurate battery reading. 

Side note:  The openings in the walls for the wiring look like they were punched out with a dull screwdriver. All the holes were ragged with splintered edges. Worst workmanship I’ve ever encountered.