Dark/fresh water senders

[Nick Epps]

Hi there, I believe I have some issues with both dark and fresh water senders. Both tanks have been cleaned very thoroughly (yep, I've been up and personal with the poo tank, and just about got over that) and the senders move cleanly, but not registering properly on the two dials in the cockpit. (both dials seem to be working ok) so I've deduced the sender being the weakest link......I have been given a quote from a well know Fairline parts supplier of £130 each plus VAT.... seems pretty full on to me. A few things I'm assuming, that I would like your guidance on. 1) are they screwed into the top of the tank or stuck? if so other suppliers use a standard thread/size? 2) the depth of the float mechanism is clearly important and I don't have that measurement to hand, so are there replacement units that can be altered to fit, or do you have to have the precise measurement/fitment. 3) any good supplier/internet suppliers options for non OEM parts. Over.... (in the middle of my VHF course)

 

[Portofino]

Wema are screwed in .Undo the wire and anticlockwise twist .
They are length specific so either get the serial number on top or measure before looking on E bay .
Some are 5 hole universal fit interchangeable but as said buy the correct L .
eg - 250mm Boat Marine Tank Level Sender Car Truck Water Fuel Gauge Sensor | eBay

They do get stuck btw .Have you tried just freeing them up .
Two ways with the black tank the £hitty job of removing it and cleaning the shaft etc .
Or go out in a rough sea and fly off the top of few waves ….this normally frees them up esp if the boats been static - winter lay up etc .Add some soapy water , flush it down about 2/3 bucket loads before wave bashing .Works every time for my black tank sender .
Yes I did many moons ago remove it .Only once .

 

[vas]

+1 on Porto,
corrosion on cables (and or connectors) could be an issue as well (both at the back of the gauge and at the sender!).
When you say don't register properly, what exactly do they show when tanks full mid empty?
Not sure but a 1kOhm potentiometer is 2euro, a sender is 100+, I'd get a potentiometer hook it up and see if gauge values registered are within range/smooth/etc. Play around a bit could help you identify the issue.

 

[Nick Epps]

Wema are screwed in .Undo the wire and anticlockwise twist .
They are length specific so either get the serial number on top or measure before looking on E bay .
Some are 5 hole universal fit interchangeable but as said buy the correct L .
eg - 250mm Boat Marine Tank Level Sender Car Truck Water Fuel Gauge Sensor | eBay

They do get stuck btw .Have you tried just freeing them up .
Two ways with the black tank the £hitty job of removing it and cleaning the shaft etc .
Or go out in a rough sea and fly off the top of few waves ….this normally frees them up esp if the boats been static - winter lay up etc .Add some soapy water , flush it down about 2/3 bucket loads before wave bashing .Works every time for my black tank sender .
Yes I did many moons ago remove it .Only once .

I've cleaned both senders and the floats move smoothly, but when I record the output on the gauge on my phone, the readings don't show any change.... they are certainly not stuck or weighed down....

 

[Nick Epps]

+1 on Porto,
corrosion on cables (and or connectors) could be an issue as well (both at the back of the gauge and at the sender!).
When you say don't register properly, what exactly do they show when tanks full mid empty?
Not sure but a 1kOhm potentiometer is 2euro, a sender is 100+, I'd get a potentiometer hook it up and see if gauge values registered are within range/smooth/etc. Play around a bit could help you identify the issue.

I will check the cables. One thing I did notice is when I disconnected the dark water tank sending all the lights on the dial lit up showing it was full, so assumed the dial was working. As for the readings, dark water tank has 3/6 lights light up, fresh water never reaches full even tho the tank is certainly full to the brim, and then seems to show empty pretty quick when its not empty. I just feel that the sender would be the the obvious part to loose its way, and a simple low cost item to replace before I tackle any further issue, if you see what I mean...

 

[vas]

true, thing is you have to make sure the sender that is fitted now is the right one (both lengthwise and Ohmwise, don't forget across the pond senders measure the opposite way, but guess wouldn't show full and then empty that way)
I mean the fresh water tank behaviour is not quite right...
undo the most likely 5 bolts on top of the tank, remove the sender, and assuming it's the typical one with the floater ring that moves up and down through the shaft, connect it again and move it fully up and down and see what's registered. Wiggle cables first, buy sender afterwards ?