12 volt ground question

I have been reading the Forum of a couple of years, however, I think this is my first post. Our Entertainment system quit working recently in our BH 3270. Since we are practicing social distancing, I decided to trouble shoot the problem. There was no power coming through the plug into the system. The fuse located on the plug tested good. Next tested the entertainment system, powered it up with a jump box and it worked. Finally figured out the ground source is not grounding. Apparently it is broken somewhere between the entertainment system and the fuse block ground. There is no other 12V in the area to tie the ground into. There are 110v plugs. Is there any reason I couldn’t use the ground at a 110 outlet to ground the entertainment system?

Thanks
jbmoto
2016 BH 3270

Hi jbmoto,

Here's the way I understand the 120V AC ground versus the 12V DC ground.

On 120V AC devices, the ground is protective. Power from the campground pedestal flows through the hot wires and returns on the neutral. Normally, the ground does nothing. It's tied back to the the pedestal so that if one of your 120V AC devices has an internal failure, instead of electrifying you, your trailer frame, or trailer skin, the leaking power flows safely through the ground wire back to the pedestal and to ground there.

On 12V DC devices, the ground wire is connected to a buss that in turn is connected to the trailer frame. The negative terminal of the battery is also connected to the trailer frame, so the negative terminal of the battery and ground wires for all 12V DC devices are connected. This allows completion of the electrical circuit between the positive and negative terminals of the battery, with your 12V device in between.

Tying the broken ground wire of your 12V DC device to the 120V AC ground wire would not complete the circuit to the battery, so I don't believe your idea would work.

In addition, there might be some abnormal conditions where tying the 120V AC wires to the 12V DC wires could produce undesired effects.

Thank you! After more trouble shooting, it was actually the power line that was comprised. I ended up wiring into the light above the TV. Good news is it works fine but we have to turn on the light to run the radio.

That undesired effect would be a fire if that ground failed and a short occured in the circuit, sending 120 VAC through your entertainment system, back through your 12 VDC system.