VDO Engine Hours Tacho Repair

Our Jeanneau 39DS has been pretty much trouble free. One annoying thing though, has been that the engine hours display which is part of the Yanmar (Type B) engine panel, only works intermittently.

Some digging on the web revealed this is a very common fault with these tacho units which are manufactured by VDO. The VDO part number is N02012195.  In fact the fault is with the display module connection itself, the meter continues to clock up hours happily in the background.

The obvious repair is to install a new meter, but I didn't want to do this for three reasons.

The first is that the boat has very low engine hours and I didn't want to loose continuity of those hours by fitting a new unit and resetting to zero hours again. It would raise a question in a future buyers mind about whether the reported total engine hours are genuine. The second reason is that the new meters are stupidly expensive and thirdly, I'm unconvinced that they have actually resolved the problem in the new meters and a future failure would seem to be only a matter of time.

Luckily I was able to track down some clever guys who have been able to replace the LCD panel with a smart OLED display driven by an Arduino Nano which interfaces with the original meter. A link to the detailed instructions is here.

I used denMikes version of the Arduino sofware, because it allowed the use of fonts for the hours display and a custom splashscreen at start up. It can do that because the OLED display is a pixel matrix rather than the LED panel which could only display digital style numbers (otherwise known as 7 segment numbers). \

I'm really happy with the results.


If I was doing the job again, here are a few tips.

There are two versions of the software in the post above, be careful that they each use different pins on the Arduino nano. My first attempt mixed these up and it didn't display anything.

I found the tacho pointer difficult to remove. Eventually I loosened the three plastic feet which attach the dial to the circuit board, then used a screwdriver between the back of the dial and the pointer motor to prise off the pointer.

It is quite tricky to align the OLED display straight, behind the cutout in the dial. Make sure you try everything out and power it up before you stick everything in place and re-assemble. On my display I needed to remove about 1-2mm of plastic from the top of the OLED cutout to make thing line up. The repair seems to work for a number of VDO tachos so your positioning may be different.

I decide to house the Nano in a little box which I stuck to the back of the tacho. I used 15cm ready made female-female jumper leads to make most of the connections. If I was doing it again I would buy a Nano without the header blocks and solder in some longer bits of wire. 15cm was only just sufficient.

I coated all the jumper lead connections and the back of the OLED display in hot glue. Its a bit messy but I thought it would provide some strain relief for the cables and also help keep any moisture out.

The solder connection to the tacho circuit board is tiny. I had to buy a magnifying glass to see it properly. If you are still reading this Good Luck with your repair !