How can we help?
Answers and how-to guides for identifying and ordering senders, testing and fault-finding, wiring, and connecting to NMEA 2000.
01 — Identify & orderFind and order the right sender
Work out exactly what you have, then order the correct replacement.
Identify a replacement sender
Work out the type, resistance, length, wires and Wema code so you order the exact replacement.
Read guide → S3 vs S5What's the difference between the S3 and S5?
Same sender, different head: the S3 screws in (1¼" BSP); the S5 bolts down to an SAE 5-hole pattern.
Read guide → LengthWhat length sender do I need?
Fuel & water: about 25–50 mm shorter than the tank. Holding tanks: no more than 75% of tank depth.
Read guide → ChartSender identification chart
Match your sender against Wema's past and present range in a single reference chart.
View chart → Older modelsDiscontinued senders
Identifying an older Wema sender that's no longer in the current range.
View list →02 — Test & diagnoseSomething not reading right?
Find out whether it's the sender, the gauge, or a resistance mismatch.
Test a sender
Disconnect it, set a multimeter to ohms, and check the reading swings across the sender's full range.
Read guide → GaugeTest a gauge
Disconnect the sender wire and earth it: a working gauge should swing fully between empty and full.
Read guide → ResistanceEuropean vs American resistance
Euro runs 0–190Ω, American 240–30Ω. Sender and gauge must match, or the gauge reads backwards.
Read guide → TachometerTachometer setup & calibration
Calibrating a Wema tachometer to your engine — the speed-ratio formula and settings, for a qualified installer.
Read guide →03 — Wiring & installationWiring it up
How everything connects. More wiring guides are being added here.
04 — Connect & convertMultiple gauges, and going digital
Run more than one gauge, or bring senders onto an NMEA 2000 network.
Two gauges from one sender — or two senders into one
When you need a Dual-Station Converter: show one tank on two gauges, or average two senders into a single gauge.
Read guide → NMEA 2000What is NMEA 2000?
The digital network standard for marine electronics — how it carries data, and what you need to build one.
Read guide →More on NMEA 2000:
05 — Replacing an old senderUpgrading from an old float-arm sender
Replacing a worn, old-style sender with a Wema tube sender.
06 — PoliciesOrders & returns
Can't find your answer?
Send us a message and we'll help — and if it's a common question, we'll add it here for the next person.
Get in touch →