The board functions 

• Temperature sensors (supply, exhaust, brine, DHW tank)

• Fan control signals

• Compressor control interconnects

• Safety interlocks

• External relay interfaces

• Communication buses (internal CAN‑like NIBE bus)

• Power‑limited auxiliary circuits

It does not contain the main CPU or firmware — it is a passive/semiactive interface board, not the main controller.

Typical Failure Symptoms

If your splice card is failing, you may see:

• Intermittent or permanent sensor error codes

• Incorrect temperature readings

• DHW tank not heating due to false sensor values

Fan or actuator issues

• Fan speed stuck at one level

• Fan not responding to control changes

• Damper/valve not actuating

Communication errors

• “Internal communication error” messages

• Random resets or loss of connection to accessories

Power‑related anomalies

• Low‑voltage supply instability

• Board warm to the touch (should normally run cool)

Physical signs

• Burn marks near connectors

• Corroded pins (common in humid installations)

• Broken solder joints on high‑stress connectors