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I enjoy puzzles, including, yes, that ultimate time waster, Candy Crush. That’s probably why I have a love-hate relationship with repair jobs on the boat. Especially ones that require me to learn something in order to solve them.

I love-hate Candy Crush!

Today I spent a couple of hours troubleshooting our generator’s non-functioning temperature gauge. I can’t actually recall if it has ever worked but if it did, it definitely hasn’t been for a long time. I have been especially interested in this since I replaced the generator’s exhaust elbow, and removed the bits of impeller that I found in the heat exchanger. With those repairs completed, and cooling water flow increased, one could assume that the gen set would be running cooler. Without a working gauge though, that’s difficult to prove.

Both Rebecca and One Love’s owner Michael have learned that I hate having people start calling out suggestions to me when I first begin troubleshooting something. They have learned to just leave me alone, and I really appreciate that. Like a puzzle, I can’t stand having someone tell me the answer until I’ve really reached an impasse. If I want or need help, I’ll definitely ask for it.

Of course, the above only applies if you’re within earshot of me when I’m working on a problem. When it comes to this blog, feel free to throw out your suggestions. I can always decided when I want to read them.

The temperature sender screws into the expansion tank.

I’ve learned that the temperature gauge by our electrical panel works much like the fuel gauges that I played with some time ago. There is a temperature sender screwed into the expansion chamber (see diagram above) which, when heated by the water flowing by it, changes resistance. This change in electrical resistance affects what the gauge reads*. Thinking that the likely culprit was the sender, I replaced that today. Unfortunately, I still didn’t get the gauge to function as it should. Fortunately, that sender was not an expensive part! That leaves either the gauge that is not working, or a messed up wire between the sender and the gauge. As both ends of the wire look to be in good shape, I am now working under the assumption that the gauge is messed up. I should have a replacement tomorrow to prove my hypothesis. We’ll know then for sure.

The old temperature sender looks almost new after I cleaned it!

*After I replaced the sender with a new one, I tested the one that I took out (photo above). By placing the leads of an ohmmeter on it, and heating the end with a lighter, I was able to see the resistance drop as the temperature increased.


  1. Mike – I’m sure you’re aware of the fact that when faced with any problem – yours or another’s – the male reaction is ALWAYS – Solve that problem. We can’t help it – it is programmed into our DNA 😉

  2. If the resistance of the sender drops as temp increases, you should be able to short the sender wire to ground and see the temp gauge swing all the way to hot.

    Remove the gauge from the panel and attach a short wire to the gauge in place of the one that runs to the sender. Touch that wire to ground and see if the gauge swings to max temp. If it doesn’t move, the problem is with the gauge. If it does, then the issue is in the wiring.

  3. Well, at least it has caused me to look up Candy Crush on Wikipedia.

    I had never heard of it before. I’m not sure that I am much the wiser having read the explanation. Maybe ‘ignorance is bliss’ is still appropriate.



  4. How about if I whisper the answer:-)

  5. You do not have to run a wire like the old one just use a piece long enough to go between the gauge and sending unit. Boats are not like houses, they live and breath, as you go pounding along the hull is always flexing. The wires can become fatigued and break in the middle of the wire, with the insulation remaining intact. By the way I really enjoy your blog.

  6. It is ALWAYS the last thing you try that solves the problem.

    I would suspect the resistance on the temp sender is such that you COULD try the spare fuel gauge just to see movement and prove the wire is good..

  7. Hi Mike,
    You can test the continuity of the wire by having someone hold the generator side of the wire to a prong on an extension cord and with your handy multimeter on the other end of the extension cord and the gauge side of the wire. With luck it will beep and save the fun of running a new wire! ps thanks for the ICW books – handy items.

  8. One option is to check the voltage between the sender wire and the sender body, and with additional ground points if you get nothing. Also check the voltage to and from the gauge. These checks might reveal a poor connection.

  9. What was the outcome with the new part? I work with heat exchangers on land and use various chemical cleaning solutions, But I have never worked with boats.
    I use condenser coil cleaners for my heat systems.
    BTW Your blog is great! Well written and full of colorful pictures.

    • Thanks, Jim. Unfortunately, I have yet to get the temp gauge working. I have replaced both the sender and the gauge. That leaves the wire itself. When I get a bit for time I’ll investigate it further.

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