Water Heater Switch Not Working
On this page (5 sections)
The Short Answer: A water heater “switch” that does nothing is usually one of three things: a tripped breaker or open disconnect feeding a home electric heater, a GFCI or power switch feeding a tankless unit, or on an RV, a missing 12-volt or 120-volt supply to the inside switch. The switch is often fine; check the power behind it. If a breaker trips again, leave it off.
Which switch do you have?
| Where it is | What it is | Common reasons it “does nothing” |
|---|---|---|
| Metal box on the wall near a home electric tank | Disconnect switch or fused pullout | Breaker at the panel is off or tripped; fuse blown; switch failed |
| No local switch, only the panel | The double-pole breaker is the disconnect | Breaker tripped (handle in the middle) |
| Wall switch or GFCI outlet near a tankless or power-vent unit | 120-volt supply | GFCI tripped; breaker off; unplugged |
| Two rocker switches inside an RV | One for gas (12 V) and one for electric (120 V) | Battery low or disconnected, coach fuse, no shore power, water heater safety tripped |
| Red button behind the upper panel of an electric tank | High-limit reset (ECO), not an on/off switch | Overheat trip; see below |
Home electric tank
A 240-volt electric water heater is usually fed by a double-pole breaker and often a local disconnect within sight of the heater. If the disconnect handle is on and the heater is cold, the breaker may have tripped; a tripped breaker’s handle often sits in the middle position.
What you can check safely: Reset a tripped breaker once by moving it fully off, then on. If it trips again, or trips after a few minutes, leave it off. A breaker that will not hold means a short in the element, wiring, or switch, and resetting it again can cause damage. See breaker tripped and won’t reset. If the area around the heater or panel is wet, do not touch the panel; call an electrician.
Do not open the disconnect box, replace fuses in a fused pullout, or remove the heater’s access panels. Those carry 240 volts.
What the electrician will check: voltage on both sides of the disconnect, the condition of the fuses and terminals (a scorched disconnect often means a downstream short), the breaker itself, and the heater’s elements and thermostats. If power reaches the heater and it still does not heat, see electric water heater not working after a power outage or the element pages.
Tankless and power-vent units on 120 volts
These units need household power for their controls and fan. If the display is dark or the fan never starts, check the GFCI outlet or wall switch, the breaker, and that the plug is fully seated. Reset a tripped GFCI once. If it trips again, especially after rain on an outdoor unit, leave it off and see tankless not working after rain.
RV water heater switches
Most RV water heaters have two inside switches: one starts the gas (LP) ignition board on 12 volts, and one powers the electric element on 120 volts. They are separate circuits.
What you can check safely:
- Gas switch with no click or light: confirm the coach battery is charged and the battery disconnect is on, then check the water heater fuse in the coach’s 12-volt fuse panel.
- Gas switch with a fault light: the switch worked; the ignition locked out. See RV water heater fault light.
- Electric switch on but no heat: confirm shore power or the generator is running and the 120-volt breaker for the water heater is on.
- Neither works: make sure the tank is full and the bypass valves are set for normal use, not winterized.
What the technician will check: voltage at the switch and at the water heater, the control board and its fuse, the high-limit and thermal cutoff, and the element. For model-specific steps, see Suburban not working on electric or Atwood electric not working.
Frequently Asked Questions
Q: Is the red reset button on my water heater a switch? A: No. It is the high-limit reset (ECO) on an electric heater’s upper thermostat, behind a panel with live 240-volt parts. It trips when the water gets too hot. Have an electrician or plumber find out why before it is reset.
Q: Can a water heater disconnect switch go bad? A: Yes, but it is often damaged by a problem in the heater, such as a shorted element that overheated the terminals. Replacing only the switch can leave the real fault in place.
Q: My RV water heater switch light comes on but the heater doesn’t light. Is the switch bad? A: Usually not. If the switch lights, it has power. A lockout light after a few tries points to gas supply, ignition, or a safety, not the switch.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith: standard electric no-hot-water diagnostic chart (opens in a new tab)Professional diagnostic context for standard electric storage heaters; not instructions to open or test your appliance.
- Suburban: service and support (opens in a new tab)Identify the appliance behind the RV badge and obtain its operating instructions.
- Dometic: product support (opens in a new tab)Product manuals and support for Dometic equipment; confirm coverage of any legacy Atwood model.
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