Phoenix's Flight: New Tank Senders and Gauges

As part of the "refit" (aka demolition) handy work performed by Phoenix's previous owner, the majority of the wires were cut, and many of the masking tape labels on the few remaining wires are illegible. Bill's been running new wire throughout the boat for both the AC and DC systems, and the time had finally come for us to tackle the tank senders and gauges.

All of Phoenix's tanks are aluminum, and from what we can tell from diagrams and other clues found on board, the tanks were replaced around the same time that the cabin tops were modified. She came equipped with older VDO adjustable arm senders and gauges, and all of the gauges were located in a panel near the nav station. The port fuel and starboard water tanks didn't have senders, but aluminum plates covered the holes where the senders should have been. We were able to locate the wires that went from each gauge to the senders, and with the aid of a volt meter, Bill determined that all the wires were good. The water and holding tank senders were definitely not registering on the gauges, and our assumption was that that starboard fuel tank sender was faulty as well, since it was always registering full when connected.

Our first thought was to simply replace the senders and keep the gauges, at least for the fuel and water tanks. We really liked the functionality, simplicity and price of the Wema senders, and noticed that they have a standard American 240-33 ohm signal output, whereas our VDO gauges needed an European 3-180 ohm input. Wema could custom manufacture senders with a different signal output, but we weren't really looking for custom orders or custom prices (especially if we need to replace them later down the road while cruising).

Due to the corrosive nature of the contents of holding tanks, we knew we wanted something different for that tank -- something without moving parts and with an enclosed system. Our friends on m/v Beach House were really happy with the Solo Tank monitor and sender they recently installed, and after doing a little homework we decided that this was the system we wanted four our tank as well. The Solo system is perhaps better known as the Scad monitor, though you can purchase directly from the manufacturer rather than through private label.

Solo makes a multi-tank LED monitor that was pretty tempting, but after looking at all of the costs, the layout of our existing gauge panel, and with a general preference for redundant, independent systems, we decided to go with new Wema analog gauges for the fuel and water tanks, and a single solo tank monitor and sealed internal PVC tube sender for the holding tank.

With our decisions made and parts in hand, it was time to pull up the floor boards and start replacing the tank senders. Theoretically this should have been the easy part. We removed the senders from the water tanks first, and much to our surprise and dismay, the hinge on the old VDO senders was not made of stainless steel, and were a rusty mess. In fact, all of the water in our port tank was orange from the rust, as was our water filter! So we had some cleaning to do. Once the water tanks were clean and the old senders thrown out, installing the new Wema senders in the water tanks was simple.

Next, we tackled the fuel tanks, and again had a bit of a surprise. Apparently the old starboard tank sender was working all along, and when we removed it, we saw that the tank was full! So we have 100+ gallons of fuel we didn't know we had (we've been running off the port tank), and our fuel polishing system upgrade has moved up the priority list!

We saved the most fun for last with the replacement of the holding tank sender, and neither of us were too excited about the prospect of opening up that tank. On the plus side, we pumped it out in the Fall before winterizing so we knew it was empty. The fuel lines running from the tanks to the engine run almost directly over the location of this sender, so we were a little worried about the logistics of removal and installation.

And, one of the previous owners had the bright idea to use brass screws to install a stainless sender into an aluminum tank. Of the 5 screws holding the sender in place, 2 were missing, 1 came out easily (was actually undersized for the hole), 1 had half of its threads corroded off, and the last was completely corroded in spot with no head remaining. We were able to pry the sender top off of the tank and drill out the last screw, but when lifting out the sender, which was completely corroded as well, it fell apart into pieces. We retrieved the top half, but the rest remains in the tank.

What remains of the holding tank sender (left) and the one working fuel sender (right). The water tank senders
were identical to the fuel sender, except the hinges on the float end were completely rusted.

With all of the senders installed, it was time to wire them up and work on the gauges. Of course the Wema gauges are not the same size as our old VDO gauges, so rather than make Swiss cheese out of our original panel, we opted to make a new panel to go in its place. This would also allow us to custom fit all of our new gauges, and add a few other gadgets like our upgraded bilge pump switch with an added audio alarm, Xantrex Link 20 battery monitor, 12V power socket, etc.