i HAVE A 2003 Mainship Pilot. the gauge is not working ? anyway i can find out if i have a bad sending unit , unable to reach the top of holding tank to check it out without having to remove the tank?
Fresh water -- and holding tank (toilet effluent) -- in the same sentence?
Anyway, our boat isn't a Mainship, but I'd guess you maybe have WEMA senders and in that era, part of the units were plastic... and known to fail after a (undertemined) while. WEMA's newer units are all stainless and apparently much more reliable over time.
If you can reach the top of the sender at all, a continuity test will give you a clue about whether yours has gone bad or not. Before you do that, though, there's also likely a 3A inline blade fuse somewhere in your system, perhaps wherever all your other fuses are located... so check that first. Could be as simple as replacing that fuse.
That said, we did have to replace our holding tank and freshwater (both) senders. The holding tank sensor was easily reached, easily replaced. (After some prior prep: pump-out, rinse, repeat a few times.)
In the case of our freshwater tanks, that sender was too long to remove from the top of our tank without cutting an access port in the space above it. In our case, that happened to be in the "floor" of a hidden storage area, so know big deal. 6" hole saw, out with the old, in with the new, covered it all with an access hatch, E Voila!
-Chris
