Erratic voltmeter readings

Often what can cause this is a very weak circuit. By that, I mean that all the wires in the circuit are not properly connected.

One way to check this is to connect a single 12 volt bulb across the circuit you are measuring. If you try that, and the bulb does not light, but your meter shows this variable voltage when the bulb is not connected, the circuit is so weak that insufficient current can run to light the bulb. The meter shows voltage because the meter is very high resistance, and only takes the tiniest amount of current.

Does your meter use a battery? Mine acts crazy when the battery is weak.

It sounds like you do not have a good connection from the 12V source to your multimeter positive or negative lead.

14V would only be read if you are charging the battery, as the rest state in lead acid is around 13 volts (perhaps as much as 13.6 volts immediately after turning off the charger.

9V would only be read if you are shopping for new batteries.

Is the camper plugged in to AC?

jimh425 wrote:
Is the camper plugged in to AC?

Yes

I suggest you first start at the battery and check for a good hard clean connection on the ground, to the chassis and then to all other places. Once those are known good, you can check for a consistent 12VDC on all devices, and again make sure of a clean hard connection.

Beware of corrosion, damaged wire/cable, bad connectors.

If it is plugged in, the charger could be causing the fluctuation. Try unplugged as well, or at least unplug the charger.

jimh425 wrote:
If it is plugged in, the charger could be causing the fluctuation.

But, while plugged in and charging, there's no reason the voltage would drop to 9 though (unless there are loose connections)

It could drop to 9 if the battery has a dead cell.

With the 120 VAC disconnected, the voltmeter reads a steady 13 and change. Sounds like the charger is the problem.