A09
IVT
Flow water temperature sensor failure
Furnace display indicates flow temperature sensor fault; burner may not modulate correctly
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Defective NTC sensor, Wiring harness damage, Sensor not in good thermal contact with flow pipe, Control board sensor circuit fault
How to Fix / Troubleshooting
Safety: Disconnect power before working inside the furnace.
- Locate flow sensor: Identify the IVT flow temperature sensor on the outlet (flow) pipe from the heat exchanger.
- Inspect mounting: Ensure the sensor is firmly attached to the pipe or inserted into its well with thermal paste if specified by IVT.
- Check wiring: Follow the sensor cable back to the control board. Look for pinched, abraded, or disconnected wires. Reseat the connector.
- Measure resistance: With the sensor disconnected and the system cool, measure resistance and compare to the IVT chart. Replace the sensor if readings are clearly out of range.
Incorrect flow temperature readings can cause overheating or poor comfort; if replacing the sensor does not resolve the issue, have the control board checked.
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Repair Difficulty
Medium
3/5
Required Part
IVT flow temperature sensor (NTC)
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