fuel tank sender unit

Hoping someone can help me. I have a sender unit in my fuel tank, however, i have a pos and neg wire just sitting on the tank not connected to anything. now i am assuming, that he sender unit should have some elec box attached to the top for the wiresto connect to. can someone advise if i am correct, and if not, what i do with regards to connecting

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grantarctic1's picture

Posts: 2546

Date Joined: 03/03/11

Some have

Fri, 2015-05-15 20:14

 Some senders have units on top with wires already conected.

With this one,I believe this diagram is corect.

Cheers Grant .. 

Posts: 13

Date Joined: 25/03/15

Thanks Grant I thought the

Fri, 2015-05-15 21:10

Thanks Grant

 

I thought the same, but when looking online for info all i could find was the negative connected to a metal thing that was apart of the sender, and the red to the centre. but mine doesnt have a metal thing to connect onto, so only thing i could think of was connects to one of the bolts, but then that seemed a little odd.

 

 

grantarctic1's picture

Posts: 2546

Date Joined: 03/03/11

Yeah

Fri, 2015-05-15 21:20

 Yeah not all have a point to conect to. Some have a flat tag for a clip to use,  alot of people wont use it because it corodes fast, and simply put the wire to one of the bolts .

So if it dosnt have a tag or screw like the one in this diagram you should run the wire to one of the bolts . 

Im not an expert tho, someone else might be able to comfirm this or not .

Posts: 13

Date Joined: 25/03/15

Thanks Grant. the wires have

Fri, 2015-05-15 21:28

Thanks Grant.

 

the wires have connectors, so can only guess that the sender has been changed at some point and who ever did this never connected (or didnt know how) as wires have connectors on them.

 

Ill solder a ring connector on both wires and connect it up and see what i get. Hate the thought of not knowing how much fuel i have in the tank once in the water.

 

cheers

just dhu it's picture

Posts: 1081

Date Joined: 14/05/09

Remove

Fri, 2015-05-15 21:39

lovejones I would remove the sender unit and take a picture to ensure the connection you thinking of doing is correct , this wiring of resistive connection to earth is okay but if this is in a Ali boat it may cause issues down the track , no Ali boat should be using the metal a an earth return connection.   IMO.   You may have to replace this unit with a unit with two terminal for correct connection  

Posts: 13

Date Joined: 25/03/15

the boats a FB, i admit i am

Fri, 2015-05-15 21:52

the boats a FB, i admit i am in two minds to just replace the unit. the gauge is a standard one also with from what i could see just 2 wires, but never been wired.

just dhu it's picture

Posts: 1081

Date Joined: 14/05/09

multi meter

Sun, 2015-05-17 14:12

 okay now its on a FB thats fine , as per grants picture you should remove the sender unit , connect a ohm or resistance meter across the centre terminal and metal plate and move the float arm up and down which will change

the resistanc reading on the ohm meter indicating the unit is operating correctly,  now connect it as per wiring diagram and test , you will now see the fuel gauge move and this will indicate where the float is inside the tank as to what 

amount of fuels available , bending the float arm will change the level or position of the float in relation to whats in the tank etc.   dont of course do this over the exposed access hatch on the fuel tank with petrol fumes present 

sarcasm0's picture

Posts: 1396

Date Joined: 25/06/09

Senders

Sun, 2015-05-17 16:26

As above test with an ohms meter. If the wires arent currently connected to anything, is there a gauge to connect them to or are you installing one? There are two types of sender/gauge - American 240-33 Ohms and European 0-180 Ohms.  Eg, if all you have is the sender you need to make sure the gauge you install or connect it to is the same ohms range as the sender, otherwise the unit will read empty when full or full when empty.  You cannot switch the wire polarity either.  The sender shown in Grantarctic's pic is ok, but in all truth the Wema captive float style are a much better design, just buy one that matches the depth of the tank, they are available in 25mm increments and either USA or European.  Eg if the tank is 200mm go for a 175mm as this will give you enough room to fit it for depth and know that even when the gauge reads empty there is a 25mm reserve. Most ones around are American but I have seen a few European ones.

Keep in mind that if the tank is long and thin in depth senders pretty much are not worth having as the angle of the boat on the plane and fuel movement make them bounce around and read inaccurately.  If this is the case, an in line fuel meter connected to your electronics may be a far more accurate way of tracking fuel usage.

Bryan