Loss of DC electric power

[stevedeiwert]

I have a 1994 25' Excella. At times the entire DC power system goes dead. This sometimes happens when 1) I disconnect the AC shore power or 2) without AC shore power I activate the power jack at the hitch.
Voltage tests show full 12+ volts at the 12 volt distibution panel, across the kill switch, etc. However, all 12 volt accessories (lights, control panel, pump, etc.) are completely dead.
12 volt power is restored when shore power is reconnected and, sometimes, when I probe around testing voltage or continuity.
Anyone know what is going on here? and how to fix the situation?

[Jammer]

There should be no voltage across the kill switch, just from the kill switch to ground.

Usually intermittent DC problems are due to corroded, dirty, or loose connections. Check both the grounds and the positive cabling. I don't give out detailed troubleshooting advice on the forums anymore (it's too easy for people unfamiliar with electrical work to get shocked or burned) but that should get you started.

[HowieE]

If you have power while the AC cord is attached you are getting that power from the convertor. That would suggest looking at the battery terminals for corrosion and a poor contact.

[Splitrock]

This might be a good time to locate, remove, inspect, clean, and reattach grounds.

[stevedeiwert]

Further diagnostics indicate the electrical problem is, in fact, a ground problem. In the 12 volt distribution panel one of the load ground blocks (the top one with the heavy black insulated wire) always shows a good solid ground connection. The two lower load ground blocks with the white and bare copper wires have intermittent ground connection. Strange? Why aren't they connected and show the same ground??

[HowieE]

In a 110 volt AC circuit the white wires are the Neutrals. The copper or green wires are Ground. The Black wire is Positive

While both white and green have the same potential at the panel code requires each be carried back to the panel as separate wires. There is never current in the Ground wires unless there is a problem and then they act as a safety.

There are no Green wires in the 12 volt DC system. DC only has positive and negative. The only way a loose wire in the AC system could effect the 12 volt system is if it cut off power to the convertor. Even then the batteries should supply 12 volts for several hours.

Again check your battery terminals if you are loosing the 12 volt system.

[Splitrock]

Originally Posted by stevedeiwert

Further diagnostics indicate the electrical problem is, in fact, a ground problem. In the 12 volt distribution panel one of the load ground blocks (the top one with the heavy black insulated wire) always shows a good solid ground connection. The two lower load ground blocks with the white and bare copper wires have intermittent ground connection. Strange? Why aren't they connected and show the same ground??

Can ya throw up a picture?

Thanks,

Gary

[TG Twinkie]

Check for fuses in the battery lead circuits. There should be at least one, it may be in or near the converter. If there is a fuse in the negative battery lead the fuse holder it is probably mounted on the skin. Make sure the fuse holders are clean and tight.

[stevedeiwert]

I have isolated the problem. It is in the load ground connections in the 12V distribution panel. The battery ground is good but the other two ground connector blocks were flaky. I have wired all three load ground blocks on the distribution panel together and the problem seems to be solved.
I still don't understand though, why the three load ground connectors were separated electrically.

Thanks everyone for your helpful suggestions.