S3U Series Threaded Fuel or Water Tank Sensor - 13"

Wema's most versatile senders are the SSS/SSL, S3U/S3, and S5U/S5 models. These single stainless steel senders typically have an NBR (Nitrile Butadiene Rubber) float, and differ only in their mounting methods.
• SSS/SSL has a basic SAE 5-hole pattern, and typically mounts with a gasket and screws
• S3U/S3 has a 1.25" BSP threaded mount, and comes in Imperial (US) and Metric (Euro) models
• S5U/S5 has a 1.5" NPT threaded mount, and comes in Imperial (US) and Metric (Euro) models
These single stainless steel models can be used with water, gasoline, hydraulic oil, or diesel.

The S3U Liquid Level Senders in this entry come with American standard outputᵠ (240 ohms at empty, 33 ohms at full) but have a BSP threaded mount so they can be used with European manufactured tanks (but not European gauges). Their length is measured in inches.

The S3U sensor has a float which rises and falls on the central shaft along with the level of liquid in the tank.
The sensor unit is fully insulated to protect against dangerous electric currents inside the tanks.
This is an extremely important safety feature, because it protects against electrolytic corrosion, as well as the danger of an explosion when used with gasoline.

The S3U sensor has 1.25" BSP - straight male British pipe - threads that seal with an O-ring.
Use this sensor with a threaded Top Adapter (FL-2WE) (see Related Products, below) which will bolt to either a standard American SAE 5-hole mount (2.125" bolt circle), or the larger European 5-hole mount pattern, on your tank.

The sending unit length is measured from the top of the threads to the tip of the gauge.
It should be at least 1" less than the depth of a plastic tank, and 3/4" less than the depth of a metal tank.*
If the top of your metal tank flexes, deduct one (1) inch from the depth (like a plastic tank).

• For use with diesel, gasoline or water
• Available in Imperial and Metric measurements – Imperial lengths in 1" increments from 4" to 60"; Metric lengths from 500mm to 1050mm
• Can be used with any Wema System dash gauge
• Sensor electrical resisitance range is 240-33 Ohms (Standard Aftermarket)
• Simple, reliable and accurate reed-switch/magnetic field design. The float is the only moving part, minimizing potential mechanical failures
• All 316 stainless steel
• Includes 38mm and 43mm O-rings for sealing
• Operating Voltage: 12/24V DC
•NBR mounting gasket (1Pc) and screw (5Pcs) included
• Custom lengths can be special ordered

American Standard Outputᵠ
Standard American gauges and senders are designed to work with a variable resistance from 240 ohms empty to 33 ohms full, while European products are designed to work with a variable resistance from 0 ohms empty to 180 ohms full. Senders and the gauges they are paired with must have the same resistance range.
The American Standard Output is non-linear and is based on American Boat and Yacht Council standards with plus or minus 5% tolerance for range difference.
Resistance readings at different levels are as follows:
• 33 ohms at 100% 
• 67.5 ohms at 75%
• 105 ohms at 50% 
• 142.5 ohms at 25% 
• 240 ohms at 0%


* Note – Fastener torque setting for mounting (with O-rings) to metal tanks is 9 +/- 1 Nm; plastic tanks is 7 +/- 1Nm