Dear customer,

Thank you for reaching out to us with your inquiry.

In response to your question directed to IHM-2319G, we are pleased to provide you with the following response.

Questions:

Is the measured resistance values 9see picture) of the heater exchanger element(s) all right?
- It's normal. In the case of general failure, the resistance value of the heater is measured very high.

How the unit detects the presence of the water?
- It does not detect the presence of water. It just converts the amount of water flowing into a frequency.
The impeller contains a magnet, and when it rotates, the hall sensor recognizes it.

Could you help with the I2C communication protocol so I could see in more detail which part of the IHM could be faulty?
- It's hard to analyze this. If there is a defect in the IHM, it is self-marked to know the cause of the defect.
For example, if the temperature sensor is defective, the LED will illuminate twice repeatedly.

What else could be wrong please (Geberit not supportive in this fault)?
- The IHM needed to be checked by our R&D team.
If many components are functioning normally, it is difficult to determine exactly where the problem lies.

The operating sequence of the IHM is as follows.

1st, transfer the set temperature from the bidet body to the IHM.
2nd, check the flow rate in the IHM and control it to the set temperature.

The parts that you checked. 
1) Heater _OK
2) Thermistor 2 type _OK
3) Flow-metter _OK
4) AC line ( thermostat and temperature fuse _OK

The following possibilities exist for the cause of the defect.
- A communication problem with bidet bodies (Main).
- Contact problems caused by corrosion of connector terminals

We hope this can help resolve the issue for you.

If you have any further questions or need additional assistance with the product, please feel free to contact us at any time.

We are happy to provide support.

Best regards

Intertec Co., Ltd