For the engine compartment I had to extend the cable of the temperature sensor to be able to mount the PCB (with the readout) outside the engine compartment. To leave the small plug intact, I soldered the two meter extension, in the middle of the cable (but first removed it from the PCB).

By extending the cable, the resistance changes slightly and the temperature value must be calibrated. This is easily done by means of the SET menu and for my situation this was only 0.7°.

The circuit board is mounted in a kitchen cabinet near the engine compartment. The temperature can be read there, without having to lift the engine hatch.

For the measuring point at the outlet of the Eberspächer heater, the standard temperature sensor cable was long enough. The circuit board is mounted in the cupboard next to it and can be read and set there.

The power cables to the circuit boards and the return line from the +12 volts to the buzzer are, per circuit board, combined in a 3 wire cable, which runs to the buzzer / LED panel. (grey in photo below) On the second picture, the temperature sensor can be seen near the heater outlet.

As an extra feature: The red glow of the readout will produce enough light to find your way at night. (without spoiling your night vision).

The sensors for water detection consist of two bare contact points per measuring point with a distance of 6-10 mm between them. They are isolated from each other on a sheet of nylon.

A sensor cable with one sensor runs to the engine compartment (under the propeller shaft). A second cable with multiple sensors runs from back to front through the rest of the ship

The panel

The panel is mounted against the window wiper motor above the steering position, so it is well noticeable while underway. When the system is “on” the green LED shows

The red LED's indicate high temperature and the blue LED's indicate water in the bilges.

When the pump of the drink water system runs, a yellow LED is on.

I chose to use one buzzer and feed it via a diode from the relay in question. With an LED, in series with a 1 kOhm resistor, I can see which alarm is on.

The power supply

It is important, for the temperature sensors and the water detector both, that the power supply voltage does not exceed 12 V. Because this happens during the charging of the batteries, I use a DC-DC converter that keeps the voltage at 12 V. One could also use other means like a more simple 7812 stabilizer.