Can I keep running the equipment with this fault active?

Generally no. Faults on Water heater units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for Rheem Water Heater High-Limit Switch / ECO Replacement Guide?

The most frequently replaced parts for Rheem Water Heater High-Limit Switch / ECO Replacement Guide are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is Rheem Water Heater High-Limit Switch / ECO Replacement Guide a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

Rheem Water Heater High-Limit Switch / ECO Replacement Guide

Q: What does Rheem Water Heater High-Limit Switch / ECO Replacement Guide mean?

Heater won't run after lockout, power cycle doesn't clear fault, or ECO trips repeatedly. Replacing the upper thermostat / ECO assembly restores operation.

Q: How do I fix Rheem Water Heater High-Limit Switch / ECO Replacement Guide?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Rheem Water Heater High-Limit Switch / ECO Replacement Guide — What This Part Does

The high-limit switch (ECO) on a Rheem electric water heater is a safety device built into the upper thermostat assembly. It monitors water temperature and cuts power to the heating elements if the sensed temperature reaches 199°F. The control stays locked out until you cycle power and the water drops below 120°F. This is not a normal operating state. It’s an emergency shutdown.

The ECO trips when actual overheating occurs, when the water temperature sensor or thermal well fails and sends a false high-temp signal, or when wiring faults create a short that mimics an overheat condition. A one-time trip after an unusual event is normal. Repeated trips or a lockout that won’t clear after power cycling and cooldown usually means the upper thermostat / ECO assembly or the temperature sensor has failed and needs replacement.

Jump to Replacement Steps

Signs It Needs Replacing

Heater locks out and won’t reset after power cycle The control stays in ECO hard lockout even after you flip the breaker and the tank has cooled below 120°F.
ECO trips repeatedly within hours or days The high-limit fault comes back every time you restore power, even though actual water temperature is normal.
No hot water and no indicator lights The heater is completely off because the ECO opened and cut power to the elements and control.
Water temperature sensor reads incorrect or erratic values Testing the sensor per the bulletin (ohms between pins 1 and 2, then 3 and 2) shows the two readings are not the same.
Visible damage or corrosion at the upper thermostat or thermal well Wiring connections are burned, corroded, or loose at the ECO / upper thermostat assembly or sensor well.
Heater ran normally then shut down without any user change The ECO tripped during normal use, indicating the safety circuit detected (or thought it detected) a dangerous overheat.

How to Replace It

Shut off power to the water heater at the circuit breaker and verify it’s off with a non-contact voltage tester at the heater junction box.
Shut off the cold water supply valve at the top of the tank and open a hot-water faucet somewhere in the house to relieve pressure.
Remove the upper access panel and insulation to expose the upper thermostat and ECO assembly.
Take a photo of all wire connections before you touch anything, then disconnect the wires from the upper thermostat / ECO terminals.
Remove the mounting bracket or screws holding the upper thermostat / ECO assembly against the tank and lift the old assembly off the thermal well or tank mounting surface.
If the water temperature sensor or thermal well tested faulty during diagnosis, remove it by unscrewing or unclipping it from the tank (some models have a threaded well, others clip in place).
Install the new upper thermostat / ECO assembly onto the tank, making sure the sensing surface sits flat against the tank wall or the thermal well is fully seated.
Reconnect all wires to the new thermostat / ECO terminals exactly as shown in your photo, then reinstall the insulation and access panel.
Restore cold water supply and bleed air from a hot tap, then turn the circuit breaker back on and verify the heater powers up without an immediate ECO lockout.

The Part You Need

Part	Notes
Rheem Upper Thermostat / ECO Assembly (High-Limit Reset)	Amazon \| Find your exact model and serial number on the data plate on the side of the tank, then cross-reference the OEM part number for your heater’s voltage and element wattage.
Water Temperature Sensor / Thermal Well	Amazon \| Only needed if sensor testing (ohms between pins per bulletin procedure) shows the two readings are not the same or if you see physical damage to the well.

If this part is failing you may also see one of these codes:

When to Call a Pro

Call a licensed electrician or water heater technician if you’re not comfortable working inside a 240V electrical panel, if diagnostic testing shows wiring faults or shorts you can’t trace, or if the ECO lockout returns after you’ve replaced the upper thermostat assembly and sensor. Repeated trips after part replacement usually mean a control board fault, a hidden wiring problem, or actual overheating caused by a failed lower element or thermostat that diagnostics didn’t catch the first time. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.