Randolf S

Hi, My MDI failed about two years after it was installed. According to Volvo, this is a known issue—the technician said he replaces about 10–12 of these MDIs every month. That pretty much says it all about the reliability of the part. Fortunately, the replacement itself is straightforward: just a few screws and unplugging and replugging the Deutsch connectors—that’s it. Nothing to be afraid of. Since then, I’ve always kept a spare MDI on board just in case—better to invest once too often than to be stranded without engine control on my next trip. The cost in Germany is about €340 (excluding the technician’s fee). Here’s an important emergency tip in case the MDI fails while you’re out on the water and you don’t have a spare part with you: You can simply bypass the connection between the battery terminal and the starter, and the engine will run even without the MDI. Important to note: the engine can no longer be shut down normally this way; instead, it must be stopped using the emergency stop switch because the MDI is dead. This at least allows you to make it safely back to port. What confirms my assessment: If you look at the part number history, there have been quite a few revisions of the MDI. To me, this is a clear sign that the part is inherently problematic and has been repeatedly modified. And when you look at the components used, it’s actually no surprise: The electrolytic capacitors used can withstand a maximum of 110 °C. The motor itself already reaches around 90 °C, and on top of that there’s the constant vibration—that’s a surefire way to kill electrolytic capacitors over time. No component can withstand that for years without failing. That’s why I’ve already considered moving the MDI to a cooler spot, like somewhere inside the cabinet. I’ve already picked up a suitable German extension cord for this purpose. So: If you have an older version installed, you should plan for a failure as a matter of “when” rather than “if,” keep a spare part on hand, and keep the workaround trick in mind.