Outdoor Current Transformer open circuit - Outdoor PCB, IPM module ×
The H16 error code on Panasonic boilers indicates outdoor current transformer open circuit - outdoor pcb, ipm module ×. Symptoms include code is displayed. (this function does not work for 3 minutes after the outdoor unit starts.
Panasonic H16 means: outdoor current transformer open circuit - outdoor pcb, ipm module ×. The usual causes are fan motor failure (seized bearings or burned windings), fan speed sensor fault or wiring fault between fan and pcb. You can safely reset the boiler once — if H16 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does H16 Mean
The H16 code is shown by the boiler’s control board when it detects outdoor current transformer open circuit - outdoor pcb, ipm module ×. 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 |
|---|
| code is displayed. (This function does not work for 3 minutes after the outdoor unit starts |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Fan motor failure (seized bearings or burned windings) |
| fan speed sensor fault |
| wiring fault between fan and PCB |
| air pressure switch fault (stuck open or closed) |
| blocked flue or air intake restricting airflow |
| condensate blocking the siphon or trap |
Safety Warning
H16 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. 1. Check of refrigerating cycle: Gas leak (Refrigerant level is very low.)
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Check for visible damage on the PCB — look for burnt components, corrosion, or water marks
Check all wiring connections to the PCB are secure
Try a power cycle — switch the boiler off at the mains for 30 seconds, then switch back on
If the fault persists after power cycling, check the error code history for related faults
Verify the mains voltage supply to the PCB is stable (230V ±10%)
Check the earth connection
How to Fix It
Replace the fan motor assembly if bearings are worn or motor is not running
replace the air pressure switch if it is stuck or reading incorrectly
clear any flue or condensate blockage
repair or replace damaged wiring
if PCB is not providing the signal, replace the PCB
Refer to the Panasonic service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
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Affected Models
Panasonic models that can display fault code H16:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Panasonic models | — | Possible |
Frequently Asked Questions
Replace the fan motor assembly if bearings are worn or motor is not running. According to the technical documentation, this is the first check on the list for H16.
H16 is not classified as a high-severity fault, so the boiler can be reset once. If H16 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.