Troubleshooting Electrical Problems in a Catamaran


A few weeks ago, I noticed someone posted a question on the Catana Owners list. The question basically asked what to do if you see the dreaded RED light on the Catana 431 digital panel? At the time I thought I would really like for someone to help me with that, and so, I waited for a response, but few constructive responses came. I saw the “There’s no voltage”, the “A circuit is broken”, and some other explanations, which are basically correct if you know what you are doing. The problem with these explanations is that they basically answered the WHAT not the how! In this short article I would like to answer the HOW for a couple of problems I ran into recently. This article will describe what I did to diagnose two electrical problems on the Catana. I hope it will help all kinds of cruising sailors with their electrical diagnosis techniques.

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A digital panel on a Catana Catamaran

The Catana digital panel, for those of you who don’t have one, moves the breakers and relays to various parts of the boat, and manages the whole thing with a digital panel that has some small boards and simple electronics on both the main panel and the distributed breakers and switches which on the Catana are called the Cartes. At first view this system is hugely intimidating to the uninitiated. I’m used to a simple breaker that looks like a breaker. In the catana there is a panel, with labels and buttons and an LED light that is either unlit, red or green. Catana owners dread the red light. This is because the company that built these digital panels in the decade of 2000 is now out of business and you can’t get support or replacements. These panels were built when Catana was one of the most successful, if not the most successful performance cruising cat in the world. So there are a lot of boats out there with completely unsupported digital panels!

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Case #1: The Shower Pump

The first of the two problems happened in the midst of a flurry of work on the boat, which included hauling out to the yard here in Cartagena. The problem happened right after the boat went in the water, so there were plenty of red herrings to chase. The failing part was the shower bilge pump. In the 431 the you take a shower and it goes into a small basin under the shower which holds about 5 gallons. After you shower you press the shower pump button next to the shower, a green light goes on, and you hear the pump start working as water is pumped out. Most of the time when this fails it just means I have to clean the filter. This time I took a most delicious shower with cool water and felt great until I pressed the button. I saw the green light come on, then off, and no gurgling sounds. I pressed again, nothing. Again, nada. Oh sh****t!

I dried up a little and with towel in hand around my waist I hopped to the panel. The panel allows you to start any pump, from that spot, which is nice. Still dripping from my shower, as I tried to figure out what button to push, I saw it! There was the dreaded RED light, waiting for me. It was laughing, saying … ha, you can’t fix me, you can’t fix me, you have no clue! Indeed I didn’t. So I put it off for a couple of days.

After a little while the water started to give a sort of unpleasant smell, so I could put it off no longer. So the first thing was to switch the hoses in the engine room and use the alleyway pump to empty the shower basin. This allowed me to see if the hose was plugged. The basin emptied with no problem.


My next thought was that it was the switch. That had to be it, it didn’t work, right? It’s the thing you press, so it makes sense. I opened up the access port, under the sink and unscrewed the button.

I then took my trusty multimeter and, looked at the device for a few seconds, wondering what exactly I should do Well my meter can test resistance, voltage, and amperage. So, what the hell. First I tested the wires that went to switch by connecting the black on the multimeter to the brown wire and the red to the blue wire. I set my meter to DC voltage and it was 12V! Good! I used the resistance meter and put it on the switch, nothing, pressed the button and “beeeeep”. This means the current passes through and it was nearly 0 Ohms, so the switch seems good. That seemed like a reasonable behavior. Press the button and 12V goes down the wire. So, now what?

The switch was now out of the circuit, so maybe the light went black? I ran up to look at the panel, it was still red. I pressed the panel button and nothing. Thinking about this a bit, that made sense to me. The switch is digital, so it sends a signal to the panel, the true switch that closes the circuit must be in the carte. So I decided that the problem must be in something that is in the circuit, which could only be the pump or the carte.

I went to the engine room, and looked at the pump. Nothing looked out of ordinary. It is a new pump. Dead end. Probably the carte. Oh no.

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I opened my Catana book and looked up the circuit, and found wire 138, shower pump (in French). There was shower something for shower on TBD (starboard), for wire 139, maybe that’s the switch, or is it something else? That’s good info. It also said that control was in Carte 4, and the manual showed that Carte 4 is in the engine room on starboard. That makes sense, the carte next to the pumps! A red light could mean something bad with the electronics in the carte!

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The carte is the one on the right

So I went to the engine room and found the carte. The Carte is just a plastic box, with a computer printed board in it, and a bunch of wires coming in and relays setup in the box. I opened it up, and behold, on the door there is map! It showed 8 circuits. I also found the wires with the 19 year old number stickers, 138, 139. They lead to P4 which seemed like the digital relay for one circuit, the shower pump. The 138 brown led to one side of P4, the 138 blue to the other and the same with 139 wire. In my mind, I figured the 139 had to be the switch, and the 138 went to the pump. I trace it and it went to the pump. The numbers near the pump had fallen off. I tested continuity and the wires matched, 138 is definitely the pump. I tested voltage but there was none.

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The map to the carte
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Under all the wiring are 8 fuses, with white amp labels and red flags!

I looked closely and each of the circuits had a fuse, so I pulled the fuse from P4. I used my trusty multimeter to test resistance on the fuse, nothing. If the fuse was still good it would beep. So the fuse had popped. I noticed that this fused seemed to have a reset, so I pushed it down, and tried again. Again nothing. I looked at the fuse, it was 10a, so went to my box, pulled one like it and stuck it in. Ha! I had it. I know I had it. I was excited! Problem solved! Feeling good.

I closed the carte, and went to look at the panel. Black. Gooooood! I pressed the button to turn on the pump, and saw a momentary green, then red. SHIT! The dreaded RED light!

I returned back to the engine room, opened the carte and pulled the fuse. I tested it with the ohm meter, and nothing. I blew this one too. I sat there for a while and thought about it for a while, I looked at the old fuse, and tested it again, and beeeeeeeep! Oh my! The old fuse IS working! I put it back in the carte and went inside. Black again.

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At this point I did not know what to do so I went to the bathroom and looked at the button and the light, and then, I figured it out. The light and the pump are in the same circuit! Wire 139 is the light! NOT THE SWITCH. So I put my hand on the light and while trying to unscrew the top, the little covering fell on my hand. I then reached into the access port and unscrewed the light socket. I tested the light and it went beep! The light looked very corroded and sad, but it had continuity. Ha! Maybe it was shorted. I taped off the ends of the wire to the light and went back to the panel. I pressed the button, and green!

OK, this makes sense! The light is 139, the pump is 138, and the light has a short in it. When I press the button, the fuse pops! They are in a parallel circuit sharing the same power source and the same fuse so with the light disconnected everything works, since no electricity runs through the shorted wire on the light socket. Problem solved, now all I need is a small light that will fit there in order to replace the corroded one.

So what I learned from this is to find the circuit on the Carte, and figure out which wires are going to it using the numbering system provided. The way they are wired onto the carte should should tell you if you are dealing with a parallel or serial circuit. A red light indicates some failure (lack of voltage) on the circuit. Troubleshooting should follow the same normal steps, to test devices, cables, continuity, voltage, amperage and fuses on each part until the defective part is found. The carte looks like magic, but it really isn’t.


Case #2: Alternating Current

A couple of days ago I was working with my window leak, and as the end of the day approached I decided to clean up. I connected my Shop Vac and started picking up dust and bits and pieces of window sealant, when out of nowhere the vacuum stopped. I ran inside to look at the panel, and there it was, the dreaded RED light on all the AC circuits. DARN! I hopped into the engine room to look at the usual circuit breaker culprits, but all of them were ON. Dammit, one more job and this one is at the end of the day.

The big bummer is that now that we have air conditioning we really depend on the cool dry air to sleep at night, and without shore power it would be a challenge to run the A/C all night.

I decided to be systematic to try and figure out what the problem was right then. First, I needed to test the power source. So I turned on the inverter, and lights were green. First good clue, it is something with the shore power, and not in the circuitry of the electric sockets.

So to take out the remaining suspects, I grabbed the multimeter, and jumped on the dock. With the breaker switches off, I disconnected power and stuck the red on one power leg, the black on the other, and yes, there was about 240V on shore power.


I have a 230V/50Hz boat, all European setup with an isolation transformer to provide 110V on board. To get 230 from shore power from American style plugs I had someone build a short conversion cable from U.S. style to the European shore power cable. I then plug into 50amp 240 power on the dock, and run it using European cable to the boat. The next suspect was that short adapter. I tested the power at the end of the legs. Also good. And the rest of the cable, good as well.

Next I went to the engine room, and looked at the mass of pumps, wires, breakers and cartes. The connection from outside to the internal wires was too high up for me to test. Nothing obvious there, and no AC cartes back here. The input box was really well wired, with no exposed wire and now easy open test door, from there it went to the isolation transformer, then to a breaker box and finally to the AC carte. The AC cartes on the 431 are under the owner’s side bunk (starboard). So I went there. There are some small black buttons on the AC carte, when a circuit pops the buttons rise. I looked at the buttons, all looked normal. I opened up the carte, and found there are no fuses like the DC cartes, so that doesn’t help. In addition, since all the circuits were showing red, either the whole carte is failing or its something much simpler.

I opened the supply box next to the AC carte, but I found no circuit breakers there, no fuses and no indication of corrosion or burning. So back to the engine room, I needed to continue to be systematic and trace the error down.

Since the wires went from the input box to the transformer, the next candidate is the transformer. My transformer was still warm and it was no longer buzzing. Maybe something went wrong with it? I texted Liem Dao (my trusty electrician) to ask whether the transformer has a fuse or internal breaker. Maybe I overloaded the circuit. He replied immediately. “NO, that Charles Isolation transformer will handle 3800 Watts!. If your vacuum was doing 1200 Watts that is not close. Your Charles transformer has no internal breaker or fuse!” That seemed pretty authoritative, so I needed to move to the next box.

I went back to staring at the mess of wires in the engine room. The AC breaker was next. The breaker can be tested without removing everything so I tried testing the 220V side. Nothing. At this time I did not test the 110V side, but that was the next logical step. If I had tested it I would have found I had voltage on that side and that it was normal!

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Next I opened up the breaker housing and there was my best chance at a culprit. There was visible corrosion and some hydraulic oil on the 220V breaker. I tested again, no voltage. I was now pretty sure this was my culprit, but now it was getting dark, and I was afraid to make a bad decision at the end of the day. So picked up some of my tools, finished cleaning up and shut down for the day. It is Friday after all, time for drinks and chicharron at the Club de Pesca (Yacht Club).

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That night (believe it or not), after drinks, I rode my bike to the Home Center (Colombia’s Home Depot), just before they closed. Two beers, plus bicycle, plus Colombia, this was probably not smart, so I made sure to have lights (but no helmet). I zipped out on my little Brompton, staying as safe as I could to pedalling on well lit streets, and traveling away from traffic. I arrived and returned safely, but only to find simple breakers. I know nearly nothing about these breakers, but I clearly can tell (using the Sesame Street method) that one is not the same as the other, one is not just the same. These breakers have four poles and extra test buttons. They are a bit reminiscent of the bathroom plugs in the U.S. with their little reset button. In Colombia they call them “differential breakers”, in the U.S. they are RCD (Residual Current Device). It is meant to protect you from accidental electrocution. It works by comparing the current between two parallel circuits, measuring the resulting magnetic field produced by both. If they do not match it breaks the circuit. Possibly the corrosion on this breaker is permanently breaking the circuit.

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On Monday morning, it took some doing for me to find the right circuit breaker. In Cartagena all the local electric supply stores are in the same avenue, next to the walled city. I went from one to the other, to another. I finally found what I needed in the last store I visited. I brought it back, cut the old one out, wired the new one in, and bingo, we are in business. The light went green, and when I powered everything up, the devices worked! Mission accomplished! Another RED light slain!

Here are my lessons learned: Systematically test devices from one end to the other; all breakers are not alike; and finally, Shop Vac vacuum cleaners draw a LOT of power!

I hope you find this tale of woe useful to your future electrical adventures. Remember that if I can find the source of my problems and fix it, so can you. You only need a good multimeter.


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