Sometimes it IS a Coincidence!

The Rules

One of the first rules of troubleshooting a complex system is:

“There are no coincidences.”

The rational here is that if multiple symptoms appear at the same time, they always have a common cause, because that is just the way things work.

Rule Two would be:

If it worked before you touched it, and now it doesn’t: You broke it.

Again, a perfectly logical rule. When something breaks, something changed. If you were messing around with the parts, it is a very good bet you did something–by mistake or by accident–that was the cause of the problem.

Here the true story of a sequence of failures we recently experienced, that proves rules are meant to be broken.

The First

While motoring recently, we had the odd experience of all our engine instruments shutting down. Using the very sophisticated diagnostic test of wiggling the key, we determined that the problem was a bad connection inside the key switch itself. Which is actually a good thing, because these are common parts and easy to get. We actually ordered it from the Volvo dealer ahead of us on Saint Martin so it would be ready when we got there.

The next day, a new symptom appears: The engine will not stop when commanded to by the key switch. This is not too surprising since we already know the key switch is on its way out. Good thing we already have one on order! In the meantime, we just have to climb down into the engine room and push the emergency stop lever. A pain, but not anything too bad. Certainly better to have an engine that is a pain to stop, but starts on command than the other way round!

All will be better when we get the new key switch.

The Second…

We arrive in Saint Martin, pick up our already paid for key switch, and install it. The problem with the instruments goes away, as expected. But the engine STILL won’t stop! Hmmmm… I must have wired things wrong. So I did a deep dive into the absolutely TERRIBLE Volvo wiring diagrams. I check, double check, and triple check everything. It is all correct.

Then I notice that the preheater is also not working. This is something we never need here in the tropics, but it is an extra clue. Careful study of the wiring diagram shows that the only common thing shared between the two systems is a ground relay. Opening up the electrical box on the engine and identifying the right relay I find that the coil of the relay shows an open circuit. How very odd. Obviously broken, but these relays are VERY reliable so this is weird. But, broken is broken! Back to Caraïbes Diesel for a relay.

And… What? A THIRD??

Install relay, and all is good. The engine starts, and stops. Except… the tachometer is not working. Well, this should be an easy one. After all, I was fussing around in the instrument panel, so I must have knocked a wire loose. I mean, see Rule 2 above. I touched it, I broke it!


It’a not a bad connection. It is actually a problem with the alternator which is where the tachometer gets its data about engine speed. I look really hard for SOMETHING connecting these problems. Because see Rule 1 and Rule 2. But there are NO connections. There is just no way ANYTHING I did could have affected the alternator. Yet, the alternator is just not working. All the tests confirm, the alternator is doing nothing. It spins, but makes no power to push into the battery. As bizarre as it seems, this is a completely separate problem not connected with the others.

We remove the alternator, and take it to the local service shop. They go through their tests, and discover a stuck brush. A simple cleaning of the internals makes it all right. In addition to having things better again, it was nice to know that if we were actually stuck in a place without the infrastructure that is here in Saint Martin, we COULD have fixed it ourselves.

Rule Rewrite

In 26 years this engine has run for nearly 10,000 hours. In the time we have owned the boat, it has run for nearly 2000 hours. It has had a few minor problems, all things we could easily diagnose and repair. Yet, in the course of only three hours of operation THREE separate–and totally independent–problems came up.What are the odds? If I had been paying a professional mechanic working on my engine, who reported this sequence of events, it would have been very hard to believe him.

So I am going to rewrite Rule 1:

“There are no coincidences–until there are.”

Trying to sort out these problems would have been a lot faster if they had occurred completely separately in time. In that case I would not have spent so much time trying to figure out how they were connected, because they HAD to be connected, right? (See Rule 1!)

The Heroes

We have two heroes in this story. First was Caraïbes Diesel on the French side of the island. They are the big Volvo Penta dealer in this part of the Caribbean. They had the parts we needed, and worked with us to be sure we got them. People (including me!) complain a lot about the prices of parts from Volvo Penta, but if you need them–and they have them–they are priceless. Thank you Isabelle and Xavier.

The staff at Electec on the Dutch side of the island was also fantastic. It is an amazing supplier of electrical parts, watermakers, and all kinds of engine oil and fuel filters. They have stuff on the shelf that you would never find anywhere else for retail pickup. The service department had our alternator sorted out in less than 24 hours. They also had–in stock–the parts we needed for our watermaker. If we had needed it, they even had an exact match for our alternator in stock.

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