04
Immergas
Primary Flow Temperature Sensor Fault (NTC Open/Short)
Display shows error 04 and the water heater will not start; may occur immediately on power‑up.
Advertisements
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.
Advertisements
Possible Causes
Defective primary NTC sensor, Broken sensor wiring harness, Poor connector contact at control board, Water ingress into sensor connector
How to Fix / Troubleshooting
Safety: Isolate electrical power before touching internal wiring.
- Locate the primary NTC: On Immergas water heaters, the primary flow NTC is usually clipped into a pocket on the primary heat exchanger outlet pipe.
- Inspect wiring: Check the two‑core cable from the NTC to the control board for cuts, burns, or crushed sections. Reseat the connector at both ends.
- Check for moisture: If there are signs of leaks above the sensor, dry the area and correct any visible seepage at unions or automatic air vents.
- Sensor replacement: If you have a compatible Immergas NTC sensor, drain the primary circuit as needed, remove the retaining clip, pull out the old sensor, insert the new one with a small amount of thermal paste if supplied, and secure it.
- Reset and test: Restore power, reset the unit, and run hot water. If the error remains, the control board input may be faulty.
Note: Measuring NTC resistance vs. temperature requires a multimeter and reference chart. If unsure, call a technician.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Primary Flow NTC Sensor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements