120v ac

Pedestal / shore power check

30 A (one hot leg): hot to neutral about 120 V, hot to ground about 120 V, neutral to ground close to 0 V.

50 A (two hot legs): leg 1 to leg 2 about 240 V, each leg to neutral about 120 V, neutral to ground close to 0 V.

Checked at the pedestal, no load

Checked at the coach, AC running (under load)

Voltage limits

Normal about 108 to 132 V. Under about 104 V under load can damage motors and compressors. Over about 132 V is too high. Always measure with a load running; a pedestal can read fine with no load.

Reverse polarity, open ground, open neutral

A plug-in outlet analyzer finds reverse polarity and open ground. An open neutral can make some loads see low voltage and others high voltage. Dangerous: check it when lights dim and brighten, or appliances act odd.

Neutral and ground

Neutral and ground must be tied together at ONE place only: the source (the shore panel or the generator). Inside the coach they stay separate. An inverter or generator can change where that bond is.

EMS / surge protector

It shuts off power for high or low voltage, open ground, reverse polarity and similar faults, then waits before reconnecting. Read its display or code, then fix the cause at the supply.

Gfci

Press TEST then RESET. One GFCI often protects other outlets downstream. Nuisance trips: moisture, a water heater element, the fridge element, a worn cord. Isolate by unplugging loads.

Breaker trips

Unplug everything on that circuit

Reset. If it trips with nothing connected, suspect wiring

Add loads back one at a time, clamp meter on the wire

Compare amps with the breaker rating (continuous loads: stay under 80 percent)

Wire and breaker sizes (copper, typical)

14 AWG = 15 A breaker. 12 AWG = 20 A. 10 AWG = 30 A. 8 AWG = 40 A. 6 AWG = 50 to 55 A.

Cord and plug

Look for discolored or melted pins, and a plug or cord end that is warmer than the rest of the cord. Heat means a high-resistance connection. Replace the plug or the cord end.

Inverter and transfer switch

Check input and output voltage separately. A transfer switch should give you shore or inverter, never both. Know which source each outlet and appliance runs from before testing.

Treat every wire as live until you have measured it. Use a meter rated CAT III. One hand when probing, and shut off the power before touching terminals. No jewelry.