Delivery/return sensor exchange
The 70 error code on Immergas boilers indicates delivery/return sensor exchange.
Immergas 70 means: delivery/return sensor exchange. On this component the documented failure modes are in the event of an error in the connection of the boiler wiring, the error is detected or the return sensor has failed — short circuit or open circuit. You can safely reset the boiler once — if 70 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does 70 Mean
The 70 code is shown by the boiler’s control board when it detects delivery/return sensor exchange. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 70 and the boiler stops until the fault is cleared |
Common Causes
The first cause below is the one the Immergas service literature publishes for this code (source: centriassistenza.org). The others are the failure modes documented for the same component on other boilers, confirmed by 4 different manufacturers.
| Cause |
|---|
| In the event of an error in the connection of the boiler wiring, the error is detected |
| The return sensor has failed — short circuit or open circuit |
Safety Warning
70 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
How to Fix It
The boiler does not start
Measure the resistance of the return sensor with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range.
Refer to the Immergas service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Immergas models that can display fault code 70:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Immergas models | — | Possible |
Frequently Asked Questions
The boiler does not start. According to the technical documentation, this is the first check on the list for 70.
70 is not classified as a high-severity fault, so the boiler can be reset once. If 70 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.