Truck & Bus Sender - TN - Wema UK
Truck & Bus Sender - TN - Wema UK
Truck & Bus Sender - TN - Wema UK

Truck & Bus Sender - TN

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The Wema Truck & Bus Sender - TN is a general purpose fuel sender incorporating suction and return pipes for fuel.

Because it is made to order and does not have interchangeable suction and return ports, like the TX sender, it is more normally used for high volume applications where a suction and return feed are required to be incorporated into the sender.

As there are so many different versions of this sender it's always best to give us a call and we can make sure that we supply you with the correct unit for your application.

The TN sender is supplied with a bolt down head with a standard SAE 5 hole pattern.

For replacement senders we need to know Wema part number.  This can be found stamped into the top of the sender.  If in doubt, send us a photo for identification. 



    • Truck & Bus Sender - TN
    • Level sensor
    • Suitable for petrol & Diesel 
    • Suction & return pipes for fuel
    • Optional Air vent
    • Optional filter
    • Optional high or low level alarm
    • 304 Stainless steel construction (body)
    • SAE 5 hole drill pattern
    • IP67

  • Torque Settings: 2.5Nm – 3.0Nm

For new applications we need to know:

    • Application (Diesel/Bio-fuel etc.)
    • Length of sensor (and/or height of tank minus 10mm)
    • Resistance value (Empty Ohm (i.e. 10) and Full Ohm (i.e.180) =>10-180 Ω)
    • Fitting for suction – dimension and/or quick fit? 
    • Fitting for return – dimension and/or quick fit? 
    • Angle of suction & return pipes
    • Air vent required?
    • Fuel filter required?
    • Alarm required?
    • Electronic connector (i.e. DIN 2-4 pin or other)

SAE-5 hole Drill Pattern

Sender Comparison Chart

To supply a replacement fuel or water sender we just need to know:


  • What is the Wema product code?

If your sender has information stamped on the head then we can identify your sender from the product code:

 Identifying a Wema sender

[Please note: the code 001300 refers to the S3 head and the code 001306 / 001305 refers to the S5 sender head]


Do you have an S3 or S5 sender?

The S3 has a screw in head with a 1.25" BSP thread like this:

[NOTE: A 1.25" BSP (British Standard Pipe) thread will actually measure larger than 1.25 inches when measured with a tape measure.  This is because a BSP measurement refers to the internal bore of a pipe (for accurate flow rate) and not the outside of the thread.] 

Wema S3 sender head

The S5 has a bolt down head with 5 holes like this:

Wema S5 sender head


[NOTE: The 5-hole drill pattern in the top of an S5 sender head is a standard SAE-5-hole pattern.] 


If you have a sender that is not an S3 or S5 then please click here


What resistance is your current sender and gauge?

The sender and gauge must have the same resistance values or the gauge will read incorrectly.

You can either test the gauge or the sender to find this out.


To test the sender:

  • Disconnect the two wires on top of the sender.

  • Remove the sender from the tank.

  • Connect the wires on the sender to a multimeter. 

  • Set the multimeter to resistance [Ω ohms]

    How to test a sender - Wema

  • Move the float to the top of the sender and take a reading on the multimeter:

    • At the top of the sender (full) the resistance should be:

      • European specification - 190 ohms

      • American specification - 30 ohms

  • Move the float to the bottom of the sender and take a second reading:

    • At the bottom of the sender (empty) the resistance should be:

      • European specification - 0 ohms

      • American specification - 240 ohms 

To test the gauge:

 If you have access to the wires on the back of the gauge;

  • Power the gauge off

  • Disconnect the black wire (sender) 

  • Power the gauge on

  • If it's an American gauge the needle will show EMPTY

    • Touch the black wire to earth, the needle will go to FULL

  • If it's a European gauge the needle will show FULL

    • Touch the black wire to earth, the needle will go to EMPTY

If you don't have access to the back of the gauge;

  • Disconnect the two wires in the loom that attach to the sender.

    • If it's an American gauge the needle will show EMPTY

    • If it's a European gauge the needle will show FULL


To measure an S3 or S3H sender (with screw in head) measure from the top of the thread to the bottom of the stem.

How to measure Wema S3 sender

To measure an S5 sender (with bolt down head) measure from the underside of the flange to the bottom of the stem

 How to measure Wema S5 sender


How many wires?

If your S5 or S3 sender has 2 wires then it is a standard resistance sender.

If your S5 or S3 sender has 3 or 4 wires then it is either a 0-5v, 0-10v sender or it has a high/low level alarm.

If you have a 3 or 4 wire sender then please contact us before ordering.

If your sender has a high or low level alarm we will need to know if the switch is normally off (when the tank is empty), turning on when the tank is full or normally on, turning off when the tank is full.  We will also need to know how far from the top or bottom of the sender you would like the alarm switch to be.


Tank Contents?

For fuel or water then you can fit the maximum length of sender for your tank.

For a black water holding tank we recommend leaving at least 50mm from the bottom of the tank regardless of the material the tank is made from.

If you tank does not contain fuel, fresh water, grey water or black water then please contact us for more specific information.  For very thick liquids like oil or grease we may need to know the viscosity.


Wema Sender Identification Chart 
    (click here for larger view)

Wema Sender Identification Chart 


NMEA2000 Products