The automatic voltage regulator (AVR) keeps a generator’s output voltage steady as the load changes. When it fails, the generator can produce no voltage, too little, too much, or an unstable output. This guide explains how to spot an AVR problem and how to choose the right replacement for your Leroy Somer alternator.

Signs your AVR may be faulty

Typical signs are no voltage when the engine runs at normal speed, output voltage that is too high or too low, voltage that swings up and down (“hunting”), or a sudden change in output after a load change. Other faults (the engine speed, the wiring, the alternator windings or the rotating diodes) can look the same, so have a qualified electrician confirm the AVR is the cause before you buy.

Step 1: Read the alternator nameplate

Do not choose an AVR by the generator alone. Read the nameplate on the alternator and note the alternator model (for example an LSA series model), its rated output and voltage, and the type of excitation it uses. Send us the old AVR’s reference too if you have it: it is printed on the AVR itself.

Step 2: Match the AVR to the alternator and its excitation system

Leroy Somer alternators are built with different excitation systems, and the AVR must be the one designed for your alternator and its excitation. The AVR references we stock are below. Each product page shows the details for that reference.

Leroy Somer AVR Approx. size (L × W × H, mm)
AVR R120 115 × 100 × 60
AVR R220 140 × 75 × 60
AVR R250 140 × 75 × 60
AVR R438 145 × 130 × 60
AVR R449 200 × 140 × 60
AVR R150 115 × 100 × 60
AVR D350 140 × 125 × 60

We also stock Genpac AVRs for other alternator makes and generator sets:

Genpac AVR Approx. size (L × W × H, mm)
AVRR450-1509 AVR 250 × 200 × 100
AVR180-1453 AVR 200 × 170 × 80
AVRHVR11-1452 AVR 170 × 120 × 100
AVRSR7-1454 AVR 150 × 120 × 70
AVRDSR-1330 AVR DSR Meccalte 150 × 120 × 70

Step 3: Fit it safely

Stop the generator and make sure it cannot start before removing or fitting an AVR. Note every wire and terminal before disconnecting, and check the wiring and the alternator with a qualified electrician. Set the voltage and stability adjustments as described in the manual for your alternator.

Not sure which AVR you need? We will confirm before you order

Send a photo of the alternator nameplate and of the old AVR and our team will confirm the correct reference.

Delivery

We ship worldwide by DHL Express. In Lebanon you can also collect free from our Beirut branch (Henry Chehab Street, facing Golf Club), Monday to Friday, 08:00 to 17:00. See our Shipping Policy for details.

Related guide: Leroy Somer Alternator Parts Guide — AVRs & Diode Assembly Kits.

Arabic version: النسخة العربية