Oso water heater shows E08 and does not heat; often occurs on models with external temperature sensors or mixing valves.

Safety first: Turn OFF power and allow hot water pipes to cool before handling sensors on the outlet line.

• Locate the outlet sensor: On some Oso models, a secondary NTC is strapped to the hot water outlet pipe or installed in a pocket near the outlet.
• Check mounting: Ensure the sensor is firmly clamped to the pipe with good thermal contact and any insulation is replaced over it.
• Inspect wiring: Follow the sensor cable back to the control board, looking for cuts, abrasions, or loose connectors. Repair or replace as needed.
• Test the sensor: Disconnect and measure resistance with a multimeter. Compare to Oso’s spec at room temperature. Replace if open, shorted, or far out of range.
• Reconnect and test: After replacing or reseating the sensor, restore power and verify that E08 clears and outlet temperature is read correctly.