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Voltmeter gauge wiring and installation instructions

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Voltmeter gauge wiring & installation

How to mount a Wema voltmeter gauge in the panel and wire it up — the diagram, the colour key for every wire, and the fitting steps.

Gauges·Installation

A Wema voltmeter drops into a 52 mm panel cut-out and wires up with four connections — power, ground, and your choice of backlight colour. There's no sender: the gauge reads the supply voltage directly, so it runs on 12 V or 24 V without any extra parts. Here's the diagram and how to fit it.

Isolate the supply before you start wiring, and double-check the connections against the diagram before powering up.

01Wiring diagram

Wema voltmeter gauge wiring diagram Tap the diagram for a larger view

02What each wire does

  • Red — to positive (battery +)
  • Blue — to ground (battery −)
  • Yellow — yellow backlight
  • Orange — red backlight

A voltmeter has no sender wire — it measures the voltage on its own supply. You only connect one of the two backlight wires — whichever colour you want lit. The wire colour matches the backlight colour it gives.

You can dim or switch the backlight, too. Fit a dimmer — a variable resistor — in line with the backlight wire to set the brightness, or wire a switch to select between the amber (yellow wire) and red (orange wire) backlight.

03Installation steps

  1. Cut a 52 mm (2¹⁄₁₆") diameter hole in the panel. You'll need a minimum clearance of 55 mm (2³⁄₁₆") behind the panel to fit the gauge.
  2. Remove the fastening ring, insert the gauge through the panel from the front, then fit and tighten the fastening ring from the rear.
  3. Connect the wires according to the diagram, choosing either the orange or yellow wire for the backlight colour you want.
  4. Insert the wire harness into the port at the back of the gauge.
A voltmeter reads whatever it's fed, so it runs on a 12 V or 24 V supply directly — no voltage regulator or dropping resistor is needed. Read the running, charging voltage rather than the resting figure: a healthy 12 V system sits at around 13.8–14.4 V with the engine running (a 24 V system reads roughly double).

The gauge

Wema gauges & displays

Analogue and multi-function gauges for fuel, water, oil pressure, voltage and more — paired with the matching sender.

Browse gauges View voltage regulators

04Common questions

What size hole does the voltmeter need?

A 52 mm (2¹⁄₁₆") panel cut-out, with at least 55 mm (2³⁄₁₆") of clearance behind the panel.

Does a voltmeter need a sender?

No. Unlike a fuel, water or pressure gauge, a voltmeter has no sender — it measures the voltage on its own power feed, so there are just four wires: positive, ground and the two backlight options.

Can I run it on 24 V?

Yes — a voltmeter runs on 12 V or 24 V directly, with no regulator or dropping resistor. It simply displays whatever the supply voltage is.

Which wire is the backlight?

Both the yellow and orange wires are backlight feeds — connect just one. Yellow gives a yellow backlight, orange gives a red one. You can also fit a dimmer (a variable resistor) in line to control brightness, or a switch to swap between the two colours.

Not sure which wire is which on your loom, or which gauge you've got? Get in touch and we'll help you wire it up.