Tuesday, September 17, 2013

Trim sensor gets a second chance.

     Sometime last summer the trim sensor on our boat started acting up. It would work for a while until the steering wheel was turned or the trim was adjusted. That was a pretty clear indication that a wire was about to break or a connection was loose. The trim sensor finally gave up and quit working. I completely ignored the issue until this week.

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     A little about the boat: Our boat is a '99 Larson LXi 186. The power plant is a Volvo Penta 4.3GL. The outdrive is a Volvo Penta SX-M.

     The trim sensor is easily accessible while the outdrive is turned to the port side. Right away I noticed that two wires were broke. I removed the two 5/16" nuts that held the sending unit in place and cut the remaining wire. After a few minutes on Google and iBoatForums I realized that this is a very common issue. Many threads discussed replacing the sending unit and gave the new part number that I needed to find and purchase a new one. The cheapest sending unit I found was on eBay and cost ~$130. 

     I am a tight wad. I could take the easy route and purchase a new sensor, but that would just be intelligent. Instead, I had ideas to fix the existing sensor. After all, why would I want to give someone $130 for what appears to be a rheostat in a poorly constructed plastic housing.

      The majority of the housing appeared to be constructed from plastic/resin. The inner portion that sealed the sending unit and wire is softer. Rather than removing all of the material, I took out enough to expose the wires:


     I have no idea what this stuff is. It's weird, because it nearly resembles a pencil eraser. Nevertheless, I used a set of small pics, and small flat-head screw drivers to rid all of this mystery material. Using picks and screw drivers, it took about one hour to expose enough wire to work with. I started with a couple of sharp pocket knifes. They seemed to work well, but I soon decided that a trip for stitches would probably be more costly than the $130 sending unit. 

     In this step, I solder a lead to each wire. I'm not re-inventing the wheel so if you aren't familiar with this, use Google. I know they're grungy looking. I cleaned them before I made the connections.

     Even after cleaning the corrosion, the solder was being a little bitch. It may have been the wind. It could have been my new iron. I'm sure it was mostly my shaky hands. I'm a bit of a perfectionist. If the wires and solder don't look just right, I start over. With this project I had my doubts. It actually worked great.

     Once installed, all I had to do was play with the trim setting and tweak the position of the sending unit using the 5/16" nuts. Although it did work, I wouldn't consider this project to be a long term solution for a failing sending unit. After soldering, the wires are stiff and (IMO) much more susceptible to failure.