The symptom that gives it away
If outlets work on shore power but lights, fans, pump or appliance controls are dead, look at the 12V side first. The disconnect switch, sometimes called a salesman switch, may be off, failed, or controlling a relay that is not closing.
What the switch really does
Many RVs do not run all battery current through the wall switch. The switch often controls a latching relay or solenoid near the battery or power center. That relay connects the battery to the coach. If the relay fails, the click may happen but power may not actually pass through.
Checks in a useful order
- Find the switch position that is labeled USE, ON, or CONNECT. Labels vary and are not always obvious.
- Measure battery voltage directly at the battery posts.
- Measure voltage at the DC fuse panel. If battery voltage is present at the battery but missing at the panel, trace the disconnect, main fuse and relay.
- Listen for a relay click when the switch is pressed. A click is a clue, not proof.
- Check the main fuse or resettable breaker close to the battery positive cable.
Why batteries still drain in store mode
Some loads bypass the disconnect: propane detectors, radio memory, solar controllers, leveling memory, breakaway circuits or aftermarket accessories. Store mode reduces draw, but it may not make the RV truly zero-draw.
When to stop
Stop if you find melted fuse holders, hot cables, unknown battery wiring or a relay that chatters. Battery current can start fires faster than most owners expect.