No question here, just a cautionary tale that somewhat might benefit from. I'll try to keep it short, though brevity is not my strong suit. Just know that this story isn't that interesting and could have been reduced to a few sentences. So, if you spend time reading it ... you've been warned.
We bought our boat about 3 months ago. We went out with the owner for a sea trial, prior to buying. On that trial, the buzzer alarm started to come on. It would kind of come and go faintly. It very much sounded like a loose wire was vibrating, causing a short, and making the alarm buzz erratically. On this boat, there are temperature and pressure switches for the alarm which are separate from the pressure and temperature sensors for the instruments. The instruments showed completely normal temperature and pressure. So, I wasn't worried about it. I figured it was an annoying loose wire. I figured the mystery would help me negotiate the price down a bit, but that it wouldn't cost me much/anything to fix.
After a while, the engine died. Acted like a fuel starvation issue.
We got it started again, but it wouldn't stay running. It finally died and would not start at all. I will fast-forward this part of the story. We ended up getting towed to a nearby marina where the survey was being performed. At that marina, a mechanic looked at it and they found that the issue was simply the fuel lifting pump wasn't receiving power. Rather than properly trace out the problem, the owner wired in a switch that allowed the skipper to turn the lifting pump on/off directly. (I'm still not sure why they didn't just wire it to the key switch, as the schematic clearly shows, but whatever. I think the issue was really that he needed to just get home, so I don't fault him for a quick but effective repair.)
I was comfortable that, being a simple wiring issue, this wasn't a deal breaker, even though it was kind of a disaster of a sea trial. Again, I figured that I could nudge the price down, but that the ultimate repair would be cheap/free. (By the way, I was right about this. But, there's more.)
We bought the boat (which was about 120 NM south of our home port). We spent about a week down there working on projects to get her ready for the trip up here.
About half way through the first day, the alarm started to come on again. So, I would check the instruments and ignore it for another 5 minutes. It would come and go, and I was looking at the instruments every few minutes. Annoying, but not especially concerning. But, after a few hours of this, it was creating tension. Even though we objectively knew that they were false alarms, every time it went off, we needed to look anyway. It finally occurred to me that, since the lifting pump was not wired to the keyed switch, but the alarm was, that I could turn the key off and enjoy some peace.
Worked a treat for about 10 minutes.
Then the engine died. Acted like a fuel starvation issue.
We were fairly close to land, but there was a little wind. So, I immediately started barking orders to get sails up so we would have control while troubleshooting the problem. Then it occurred to me. One of the last projects I did before leaving was to correctly wire the lifting pump into the keyed switch. So, if the switch was on, the pump was running - per the schematics. In other words, it was working exactly as designed, but I was already used to the pump being wired separately.
I turned the key back on, she fired right up, and we were right as rain. But, the alarm was back. So, I finally decided to just disconnect the buzzer itself. We would lose the benefit of the alarm, but since I was pretty much glued to the engine instruments anyway, that was probably OK. And, it was.
But, this gets to the point of the story. The alarm has two inputs: one from the oil pressure switch and one from the water temperature switch. The water temperature switch activates a constant alarm, whereas the oil pressure switch activates a pulsing alarm. We were getting a constant alarm. (It was coming and going, but when it was on, it was not pulsing.) So, I deduced that, at worst, it was trying to alert us to high coolant temperature. And, I knew (from experience) that if the coolant overheated, steam would billow from the engine compartment before all of the coolant had boiled away - giving us time to shut down and fix the issue.
(How I knew this is the subject of another story.)
So, we motored another 2-3 hours to our first port of call. No events. In fact, we motored about 75% of the total distance over the next few days, all without incident.
When we got home, I decided to address this issue. Again, I assumed this was a loose wire, somewhere between the temperature switch and the alarm. This wiring route was not particularly accessible. So, I decided to do a little troubleshooting with my wallet. Since the alarm was only going off sporadically, I knew that I could spend hours trying to replicate and pinpoint the problem. So, just to rule out a faulty alarm buzzer, I bought a new one. At $30 or so, I figured my time was worth at least that.
I replaced the alarm. When I had disconnected the old alarm, I carefully labelled which wire connects to the constant terminal and which connects to the pulsing terminal, on the alerm buzzer. So, when I installed the new alarm buzzer, I was able to hook it up the same way. (This is an important point.)
But, after some time, the buzzing came back. I disconnected the new buzzer and decided to dig into this later. The other easy fix was to replace the temperature switch. So, I ordered one. Another $30 or so would rule that out. If this still didn't fix it, then I knew I had to meticulously trace the wiring and find the actual problem buried somewhere in the bowels.
Then, it occurred to me that I could disconnect the wire from the temperature switch. That way, I could keep the oil pressure alarm, even though the temperature alarm was disconnected. This is something I should have thought of MUCH earlier.
But, disconnecting the temperature switch, at the switch, the alarm did not go away. It came back - a constant buzzing. I double-checked the manual. Yes, a constant alarm does indicate a high water temperature. But, the wire was completely disconnected from the switch.
"Ah ha!", I thought. This means that the wire from the temperature switch to the alarm was shorting out and getting powered by some other wire, somewhere. Right?
So, if I disconnect the high temperature wire from the buzzer, it should go away. I couldn't remember which was which, and didn't have the diagram that came with the new buzzer, so I looked this up in the manual for the engine. The schematic shows which color is which. It showed the tan-colored wire connects to the constant terminal and is wired to the temperature sensor. So, I disconnected that wire.
But, the alarm did not go away. It was still a constant alarm. How could this be? I had just connected the only wire to the constant terminal on the alarm buzzer. Unless this brand new alarm was faulty, it was completely imposssible. I was stumped.
So, I went ahead and removed the other wire (a blue one). The constant alarm went away.
I looked carefully at the alarm buzzer and saw a tiny "C" and "P" on the terminals. The tan (temperature) wire had been wired to the pulsing terminal ("P"), and the blue (pressure) wire had been wired to the constant terminal. Apparently, the previous owner, in an attempt to troubleshoot this mystery alarm, had reconnected these backward. The problem was not with the temperature switch circuit. It was with the oil pressure switch circuit.
That is the moral of this story. I had incorrectly assumed that the alarm was correctly wired when I got it. So, rather than verify this very basic fact, I incorrectly wired the new one and I spent hours/days/dollars barking up the wrong tree.
Realizing what had happened, I flipped the wires around on the buzzer to their correct terminals. Then I figured I would have a quick look at the oil pressure sensor. Took me a few minutes to find it, per the manual. It was located in a position I couldn't see directly. But, I could reach my hand in there and feel ... a disconnected wire terminal. One of the wires was just hanging there. I plugged it back in, fired up the engine, and problem solved.
After all of that, it was just a matter of reaching in and plugging in a loose wire. Had I correctly traced the problem to the oil pressure circuit, from the beginning, this would have a been a free 30-second fix.
I guess the point of all this is to serve as a reminder that even when the problem seems apparent, you should go through methodically and take out any assumptions, no matter how safe those assumptions seem. I had assumed that, since I hadn't flipped those wires around, they must be corrrect.
We bought our boat about 3 months ago. We went out with the owner for a sea trial, prior to buying. On that trial, the buzzer alarm started to come on. It would kind of come and go faintly. It very much sounded like a loose wire was vibrating, causing a short, and making the alarm buzz erratically. On this boat, there are temperature and pressure switches for the alarm which are separate from the pressure and temperature sensors for the instruments. The instruments showed completely normal temperature and pressure. So, I wasn't worried about it. I figured it was an annoying loose wire. I figured the mystery would help me negotiate the price down a bit, but that it wouldn't cost me much/anything to fix.
After a while, the engine died. Acted like a fuel starvation issue.
We got it started again, but it wouldn't stay running. It finally died and would not start at all. I will fast-forward this part of the story. We ended up getting towed to a nearby marina where the survey was being performed. At that marina, a mechanic looked at it and they found that the issue was simply the fuel lifting pump wasn't receiving power. Rather than properly trace out the problem, the owner wired in a switch that allowed the skipper to turn the lifting pump on/off directly. (I'm still not sure why they didn't just wire it to the key switch, as the schematic clearly shows, but whatever. I think the issue was really that he needed to just get home, so I don't fault him for a quick but effective repair.)
I was comfortable that, being a simple wiring issue, this wasn't a deal breaker, even though it was kind of a disaster of a sea trial. Again, I figured that I could nudge the price down, but that the ultimate repair would be cheap/free. (By the way, I was right about this. But, there's more.)
We bought the boat (which was about 120 NM south of our home port). We spent about a week down there working on projects to get her ready for the trip up here.
About half way through the first day, the alarm started to come on again. So, I would check the instruments and ignore it for another 5 minutes. It would come and go, and I was looking at the instruments every few minutes. Annoying, but not especially concerning. But, after a few hours of this, it was creating tension. Even though we objectively knew that they were false alarms, every time it went off, we needed to look anyway. It finally occurred to me that, since the lifting pump was not wired to the keyed switch, but the alarm was, that I could turn the key off and enjoy some peace.
Worked a treat for about 10 minutes.
Then the engine died. Acted like a fuel starvation issue.
We were fairly close to land, but there was a little wind. So, I immediately started barking orders to get sails up so we would have control while troubleshooting the problem. Then it occurred to me. One of the last projects I did before leaving was to correctly wire the lifting pump into the keyed switch. So, if the switch was on, the pump was running - per the schematics. In other words, it was working exactly as designed, but I was already used to the pump being wired separately.
I turned the key back on, she fired right up, and we were right as rain. But, the alarm was back. So, I finally decided to just disconnect the buzzer itself. We would lose the benefit of the alarm, but since I was pretty much glued to the engine instruments anyway, that was probably OK. And, it was.
But, this gets to the point of the story. The alarm has two inputs: one from the oil pressure switch and one from the water temperature switch. The water temperature switch activates a constant alarm, whereas the oil pressure switch activates a pulsing alarm. We were getting a constant alarm. (It was coming and going, but when it was on, it was not pulsing.) So, I deduced that, at worst, it was trying to alert us to high coolant temperature. And, I knew (from experience) that if the coolant overheated, steam would billow from the engine compartment before all of the coolant had boiled away - giving us time to shut down and fix the issue.
(How I knew this is the subject of another story.)
So, we motored another 2-3 hours to our first port of call. No events. In fact, we motored about 75% of the total distance over the next few days, all without incident.
When we got home, I decided to address this issue. Again, I assumed this was a loose wire, somewhere between the temperature switch and the alarm. This wiring route was not particularly accessible. So, I decided to do a little troubleshooting with my wallet. Since the alarm was only going off sporadically, I knew that I could spend hours trying to replicate and pinpoint the problem. So, just to rule out a faulty alarm buzzer, I bought a new one. At $30 or so, I figured my time was worth at least that.
I replaced the alarm. When I had disconnected the old alarm, I carefully labelled which wire connects to the constant terminal and which connects to the pulsing terminal, on the alerm buzzer. So, when I installed the new alarm buzzer, I was able to hook it up the same way. (This is an important point.)
But, after some time, the buzzing came back. I disconnected the new buzzer and decided to dig into this later. The other easy fix was to replace the temperature switch. So, I ordered one. Another $30 or so would rule that out. If this still didn't fix it, then I knew I had to meticulously trace the wiring and find the actual problem buried somewhere in the bowels.
Then, it occurred to me that I could disconnect the wire from the temperature switch. That way, I could keep the oil pressure alarm, even though the temperature alarm was disconnected. This is something I should have thought of MUCH earlier.
But, disconnecting the temperature switch, at the switch, the alarm did not go away. It came back - a constant buzzing. I double-checked the manual. Yes, a constant alarm does indicate a high water temperature. But, the wire was completely disconnected from the switch.
"Ah ha!", I thought. This means that the wire from the temperature switch to the alarm was shorting out and getting powered by some other wire, somewhere. Right?
So, if I disconnect the high temperature wire from the buzzer, it should go away. I couldn't remember which was which, and didn't have the diagram that came with the new buzzer, so I looked this up in the manual for the engine. The schematic shows which color is which. It showed the tan-colored wire connects to the constant terminal and is wired to the temperature sensor. So, I disconnected that wire.
But, the alarm did not go away. It was still a constant alarm. How could this be? I had just connected the only wire to the constant terminal on the alarm buzzer. Unless this brand new alarm was faulty, it was completely imposssible. I was stumped.
So, I went ahead and removed the other wire (a blue one). The constant alarm went away.
I looked carefully at the alarm buzzer and saw a tiny "C" and "P" on the terminals. The tan (temperature) wire had been wired to the pulsing terminal ("P"), and the blue (pressure) wire had been wired to the constant terminal. Apparently, the previous owner, in an attempt to troubleshoot this mystery alarm, had reconnected these backward. The problem was not with the temperature switch circuit. It was with the oil pressure switch circuit.
That is the moral of this story. I had incorrectly assumed that the alarm was correctly wired when I got it. So, rather than verify this very basic fact, I incorrectly wired the new one and I spent hours/days/dollars barking up the wrong tree.
Realizing what had happened, I flipped the wires around on the buzzer to their correct terminals. Then I figured I would have a quick look at the oil pressure sensor. Took me a few minutes to find it, per the manual. It was located in a position I couldn't see directly. But, I could reach my hand in there and feel ... a disconnected wire terminal. One of the wires was just hanging there. I plugged it back in, fired up the engine, and problem solved.
After all of that, it was just a matter of reaching in and plugging in a loose wire. Had I correctly traced the problem to the oil pressure circuit, from the beginning, this would have a been a free 30-second fix.
I guess the point of all this is to serve as a reminder that even when the problem seems apparent, you should go through methodically and take out any assumptions, no matter how safe those assumptions seem. I had assumed that, since I hadn't flipped those wires around, they must be corrrect.
