How to bypass generator AVR

BISON will discuss why it is necessary to bypass the generator AVR and explain the step-by-step bypass procedure for portable generators and backup generators.

November 26, 2025
BY BISON

AVRs contribute to the increased dependability and user-friendliness of generators, and as a result, they are currently present in practically all generators on the market. As a professional generator manufacturer, we understand that there are situations when people consider bypassing an AVR—such as during emergencies, when the AVR fails, or when replacement parts are expensive or hard to find. While bypassing can provide temporary power, it carries significant risks if done incorrectly.

In the blog, BISON will discuss why it is necessary to bypass the generator AVR and explain the step-by-step bypass procedure for portable generators and backup generators.

What is an AVR and how it works

An automatic voltage regulator (AVR) is a crucial component in every generator. Its main role is to maintain a stable output voltage regardless of changes in load or engine speed. Without an AVR, voltage can fluctuate, potentially damaging sensitive equipment or causing generator failure.

The AVR works by sensing the generator’s output voltage and comparing it to a reference level. If the voltage is too high or too low, the AVR adjusts the excitation current sent to the exciter field, controlling the strength of the magnetic field in the alternator. This process regulates the generator’s output voltage. The difference between the actual output and the reference voltage, known as the error voltage, is continuously corrected by the AVR to ensure stable power delivery.

It is important to note that AVRs can fail due to overheating, moisture, poor component quality, or power surges. When this happens, the generator may lose its ability to regulate voltage, which can harm connected equipment and the generator itself. In such cases, temporary solutions like AVR bypass are sometimes considered.

When (and when not) to consider bypassing the AVR

Situations where a temporary AVR bypass may be considered

Emergency power restoration during outages (short-term, life-safety, or mission-critical loads).
Remote or off-grid locations where AVR replacement is impossible or delayed.
Diagnostic testing to determine if the AVR is the cause of voltage issues (for experienced technicians only).
Short-term cost containment when a verified, safe temporary fix is preferable to shutting down operations.
Controlled test runs with minimal, non-sensitive loads to check alternator and field health.

Situations where you should NOT bypass the AVR

Long-term or permanent operation (bypass is only a temporary solution).
When powering sensitive electronics, medical devices, or precision equipment (risk of damage).
If bypassing violates warranty terms or local regulations.
Without proper electrical knowledge, tools, or personal protective equipment (PPE).
When loads cannot be isolated or safely shed, uncontrolled voltage may cause fires or equipment failure.
If residual magnetism is absent or the alternator has other mechanical/electrical faults, bypassing will not resolve the root issue.

List of tools and materials needed to bypass the AVR

AVR-specific tools	General tools
Voltmeter/True-RMS multimeter	Insulated electrical gloves
Insulated probes	Safety glasses/face shield
Potentiometer	Hearing protection
12V battery (optional)	Socket set & wrenches
Insulated alligator clips	Heavy-gauge extension cords/jumper leads
Clamp meter (recommended)	Flashlight or headlamp

Safety precautions before you start

Power down completely — Turn off the generator and allow the engine to stop fully before touching any electrical components. Let the unit cool for 10–15 minutes if it has been running.
Disconnect all loads — Unplug appliances and isolate the generator from transfer switches or circuits to prevent back-feeding and accidental damage.
Wear proper PPE — Add flame-resistant clothing and a face shield when working on live terminals.
Work in a safe environment — Ensure the area is dry, well-lit, and free of clutter.
Identify key components — Locate and clearly mark the AVR, rotor, and exciter field terminals before making any temporary connections. Incorrect wiring can cause reverse polarity and permanent alternator damage.
Isolate/lock out the power source as much as possible — Probe for live parts with one hand and keep metal tools away from live terminals.
Avoid working alone — Have a second person nearby to assist in case of emergency.

How to bypass the AVR on a standby/home generator

Step 1: Access and disconnect the AVR

Open the generator panel to locate the AVR module and its connections.

Carefully disconnect the AVR from the exciter/rotor circuits.

Make sure you clearly remember all terminals to ensure proper reconnection.

Step 2: Identify the f1 and f2 terminals

Standby generators usually have f1 and f2 terminals on the exciter field for external control.

Verify polarity and confirm which terminal is positive and which is negative. Miswiring can damage the generator.

Step 3: Set up the 12V battery and potentiometer

Connect a 12V battery in series with a potentiometer to the f1/f2 terminals.

Set the potentiometer to minimum resistance before connecting to avoid sudden overvoltage.

Double-check polarity and secure all connections with insulated clips.

Step 4: Startup and adjustment

Start the generator with no load connected.

Slowly adjust the potentiometer while monitoring output voltage with a voltmeter until the desired level is reached.

Gradually apply minimal loads, ensuring voltage remains stable.

Once the generator reaches rated speed, fine-tune the potentiometer to achieve rated voltage.

Step 5: Consider residual magnetism

Some generators require residual magnetism to build excitation. If lost, a brief 12V battery pulse may restore it.

Always follow correct polarity and avoid reverse connections to prevent rotor or stator damage.

Important notes: After bypassing the AVR, voltage may be lower than normal (e.g., 180–190V for average loads).

How to bypass the AVR on a portable generator

Step 1: Access the stator and AVR

Open the generator housing to locate the stator, AVR, and rotor/exciter field terminals.

Clearly label each terminal block to avoid confusion during reconnection.

Step 2: Disconnect the avr

Carefully disconnect the wires connecting the AVR to the exciter field.

Most AVRs are kidney- or rectangular-shaped and attached with two 7 mm bolts; loosen and remove them.

Ensure no wires touch the stator, rotor, or metal parts to prevent shorts.

Step 3: directly connect the rotor

Using insulated alligator clips or jumper leads, connect the exciter field directly to the rotor, following the manufacturer’s wiring polarity.

If residual magnetism is low, a 12V battery can briefly energize the field — always observe correct polarity.

Step 4: Start the generator and monitor the output

Start the generator without any load.

Use a voltmeter or multimeter to monitor voltage output carefully.

Gradually apply minimal loads to verify stability. Do not connect sensitive or high-power equipment.

Step 5: Reconnect loads carefully

Once voltage is stable and within safe limits, reconnect loads gradually, continuing to monitor for fluctuations.

Important notes after bypassing the generator AVR

Monitor the load carefully: Avoid connecting high-power or sensitive electronics. Apply loads gradually and observe voltage stability. Ensure the generator is appropriately sized for the load.
Watch engine rpms: Irregular or fluctuating speeds can indicate unstable voltage. Maintain the engine at its recommended speed for consistent output.
Make manual adjustments slowly: When using a potentiometer or manual excitation, adjust incrementally while checking voltage with a multimeter. Sudden changes can damage the generator or connected appliances.
Observe fuel consumption: Avr bypass may increase fuel usage due to less efficient voltage regulation. Keep fuel levels adequate to avoid interruptions.
Limit operation time: As a temporary measure, prolonged operation without a functional AVR may damage the generator and connected equipment.
Keep logs: Track voltage, load, and operating time. This will facilitate maintenance or repair by technicians.

Summary

We can temporarily bypass the generator AVR to obtain power in emergencies, power outages in remote areas, or unexpected AVR failures. However, this is strictly a short-term solution. Operating a generator without a functioning AVR carries risks, including unstable voltage, potential damage to connected equipment, and increased wear on internal components. Therefore, replacing the AVR or performing safe maintenance should always be a priority.

BISON offers high-quality generators, generator AVRs, and other generator parts. As a trusted generator manufacturer in China, we possess comprehensive product manufacturing solutions and equipment. Every detail, from spare parts to the generator itself, undergoes professional testing to ensure optimal performance and durability in the hands of our users.

Start a business partnership with BISON now and jointly enhance our excellent reputation in the industry!