Girard Water Heater: “E0”
warning RV water heater fault codes
What it means
The outlet (hot side) water temperature sensor reads an invalid value. The control board sees either an open circuit or a short in the outlet temperature probe and cannot trust the reading, so it faults out.
Most likely causes
- Loose, corroded, or disconnected connector at the outlet temperature probe most likely
- Damaged or chafed wiring between the probe and the control board common
- Failed outlet temperature probe (out-of-spec resistance, open or shorted) common
- Faulty control board input rare
Safe checks you can do yourself
- Turn the heater off at the wall control and let it cool before inspecting anything.
- Reseat the connector at the outlet temperature probe and at the control board; look for corrosion or bent pins.
- Visually inspect the probe wiring for chafing, pinching, or rodent damage.
- If you have a multimeter, confirm the probe is not reading a dead open or a dead short (a healthy thermistor shows a finite resistance that changes with temperature).
How to reset / clear E0
- Switch the water heater off at the user control panel.
- Turn off the heater's 12V power for about 10 seconds, then restore it.
- Switch the heater back on and run hot water to see if the code clears.
When to call a technician
If reseating connectors and a power cycle do not clear the code, or you are not comfortable testing the probe with a meter, have a qualified RV technician test/replace the outlet probe or board.
Applies to
GSWH-2 · 2GWHAM
FAQ
What does Girard Water Heater code "E0" mean?
The outlet (hot side) water temperature sensor reads an invalid value. The control board sees either an open circuit or a short in the outlet temperature probe and cannot trust the reading, so it faults out.
How do I reset Girard Water Heater E0?
Switch the water heater off at the user control panel. Turn off the heater's 12V power for about 10 seconds, then restore it. Switch the heater back on and run hot water to see if the code clears.
What is the most common cause of E0 on a Girard Water Heater?
The most likely cause is loose, corroded, or disconnected connector at the outlet temperature probe.
Related · Girard water heater
Ignition failure. The igniter sparked but the board never co… E2
Flame sensing was interrupted during normal operation. The b… E3
The ECO (energy/over-temperature cut-off) thermostat opened,… E4
The inlet (cold side) water temperature sensor reads an inva… E5
Blower/fan motor fault. The control board commanded the comb… E6
Over-temperature condition. The outlet water temperature exc…
Sources
- Girard Products GSWH-2 Technical Manual — GSWH-2 Technical Manual, troubleshooting / fault code section (E0 outlet temperature probe) (Girard Products / ManualsLib)
- Girard GSWH-2 Tankless Water Heater Technical Manual and Troubleshooting Guide — Fault code list, E0 Water Outlet Temperature Probe failure (Manuals.plus)
Note: Some sources label E0 simply as the outlet temperature probe fault; the underlying diagnostic is open/short detection. Resistance test values are not reproduced here — consult the manual's resistance table for exact specs.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.