Voltage Regulators

Is your battery not charging, or is it boiling over after a ride? Then the voltage regulator may be the cause. Here we bring together regulators and rectifiers for motorcycles and ATVs that convert the power from the stator and keep the charging voltage stable, so the battery and electronics are not damaged.

What does a voltage regulator do?

On many motorcycles and ATVs, the stator supplies alternating current, which the regulator rectifies into direct current and limits to a voltage the battery can handle. That is why the part is often called a regulator/rectifier. A faulty regulator can show up as a battery that does not charge, lights that fluctuate with engine speed, or an excessive charging voltage that can dry out and ruin the battery.

How to choose the right regulator

Fitment decides most of it, so start from your vehicle rather than from the part itself:

• Model and year: many regulators are made for specific models, e.g. from QuadBoss for the Suzuki LT-A700X KingQuad and Polaris Sportsman 450/570, or from Arrowhead for Arctic Cat and Kawasaki.
• OEM number: some products state which original part number they replace, e.g. the TwinPower regulators for Softail and XL.
• Current rating: the amperage, e.g. 22 or 38 amps, must match the charging system. A higher value is not automatically better.
• Connector and mounting: check the connector type, number of wires and mounting.

The category also includes parts from REDARC and BikeMaster.

Measure before you replace

First fully charge the battery with a battery charger, so a weak battery does not give a misleading result. Then measure the voltage across the battery with a multimeter at idle and at higher revs, and compare with the value in the workshop manual. At the same time, check connectors and ground connections, as corrosion can cause heat and voltage drop.

Frequently asked questions

How do I know whether the regulator or the stator is faulty?

Measure the charging voltage at the battery with the engine running. If it is too high, that typically points to the regulator. If it is too low, the stator, the regulator and the connections can all be the cause. The stator can be measured separately according to the workshop manual.

What does the amperage on a voltage regulator mean?

It indicates how much current the regulator is rated for. It should match the vehicle's charging system, so choose by OEM number or the manufacturer's specification rather than simply the highest value.

Why can a new regulator fail again shortly after replacement?

Typical causes can be corroded or loose connectors, a poor ground connection, a faulty battery or a fault in the stator. Find and fix the underlying fault before fitting the new regulator.