AVR or Capacitor problem
The information contained in our websites is designed as a guide only, for assisting Repair Professionals. By using our information you are agreeing to our T&Cs.
Turn off the Generator immediately and do not run if you have high voltage output as this might cause damage to the Alternator!
***If there was any smoke, or electrical burning smell from the alternator, please run the tests at the bottom of the page before replacing any Parts!
If you replace the AVR/Capacitor or Brushes for a second time, this is a sure indication of an alternator or overload issue.
**If your engine stops when you turn on the breakers or you are getting approximately half power, please submit a support ticket for more help at the bottom of this page.
Please be aware that a blown AVR/Capacitor may not be the original fault, but may indicate a fault within the alternator or an overload surge.
If you replace the AVR/Capacitor or Brushes for a second time, this is a sure indication of an alternator or overload issue.
Unfortunately, testing Generator AVRs and Capacitors, without specialist equipment, is not possible. This is because AVRs and capacitors have a tendency to show as working correctly on the low voltages that Multimeters give out. They may test correctly, but when put under high voltage or heat the fault will be exposed.
But….. we have developed tests to rule out all the other faults with your generator, enabling you to pinpoint what needs replacing!
Please note: These tests do not rule out faults on equipment that has been plugged into the generator, or that an overload of the generator caused the problem. See this article to see how much power your Generator should give out on an ongoing basis. It might not be what you expect or as stated on the generator!
If you replace the AVR/Capacitor for a second time, or wish to confirm this is not a result of an underlying problem within the alternator, please run the tests at the bottom of this guide.
The most common reasons for alternator parts failing:
1) Overloading the generator – Breakers do not protect you from overloading, only from surges.
Be sure to take surges into account when calculating what can be run on your generator. Please be aware many things with a motor could have as high as a 100% surge value to their running watts (i.e. Fridges/Freezers, Compressors, non-soft start AC). Also, be aware, most things that produce heat are at least 1500w (i.e. coffee maker, hair dryer, kettle). Also, welding often requires higher currents than portable generators will produce, it is better to use a welder generator than to power a welder with an ordinary portable generator where overload is very likely.
2) Starting the generator with equipment plugged in and breakers on – Turn off all Breakers and unplug all the equipment when starting (This is a very common reason for overloads!).
3) The Generator was not grounded. All generators should be grounded during operation as per instructed in the manual. If there is a surge it needs to go to ground to prevent damage to the alternator and prevent electrocution!
4) Equipment powered by the generator has an electrical fault and is surging beyond the capacity of the alternator.– All equipment should be tested on a regular basis. If you can smell the electrical burning scent around equipment, or issues only happen when certain equipment is plugged in, this is a good indication of an electrical fault within that equipment, or the equipment may require more power than the generator can produce.
5) Generator was manufactured or fitted with an inferior quality Capacitor/AVR and this has degraded – Not uncommon, especially on budget versions.
6)Your generator is unbranded, rebranded, and is not actually the Wattage it has been marketed to be – This is common with cheap generators bought on eBay, Amazon, random small websites or from “on the side of the road” independent vendor types. If you think the generator is small in size or very cheap compared to other similar wattage generators, there is a good chance it has been incorrectly labeled as a larger generator. Please contact us for more info and we may be able to identify it for you.
7)You have a single phase generator that has been rebranded as a 3-phase generator – Again, common with cheap generators bought on eBay, Amazon, random small websites or from “on the side of the road” independent vendor types. A common feature for some of these incorrectly marked generators is a red socket on the control panel. Please contact us for more info and we may be able to correctly identify it for you.
Only replace the part with a quality Grade "A" replacement that is built for your Generator
Anything else could cause damage to your Alternator, resulting in the Alternator needing to be replaced Cheaper parts could surge and cause damage to your Alternator, resulting in the Alternator needing to be completely replaced, a very, very expensive repair! This is why we only sell maintenance quality grade “A” products.
Do I have an AVR or a Capacitor?
Use the table below to determine where to find the part on your Generator. Also, check for burning on the Stator windings or electrical burning smells while locating the AVR/Capacitor. If you have either of these problems, run the Alternator Test at the bottom of the page before replacing.
Once you remove the AVR/Capacitor you can identify it with this table:
2 or 4 wires = Capacitor and Brushless alternator. Search our Capacitors or search by Generator Brand
5 or more wires = AVR and Brushed alternator. Search AVR by Generator Brand and Model
Once you have identified if it is an AVR or a Capacitor, look up and purchase your replacement parts on our website.
If you have an AVR on your Generator we also suggest you check the Brushes (tests below).
Where to find the AVR/Capacitor
Framed Generator
If your Generator sits in a frame, it is most commonly behind the end cover of the alternator. In rare cases, it can be found behind the control panel, follow the wires up from the alternator. It will be held on with either 2 bolts or a cable/zip tie. Replacing this should fix your problem.
Super Silent Generator
You can usually find this behind the rear panel of super-silent units. In rare cases, it will be located at the end of the alternator, if so you will need to remove the exhaust system to access it. It will be held on with either 2 bolts or a cable/zip tie. Very occasionally, manufacturers run very long wires to position the AVR so it is accessible through the service panel. Replacing this should fix your problem.
2 Stroke/Cycle Generators
In most cases, the part will be found behind the control panel. To locate it, remove the fuel tank. It will be a black box with 2 wires going to it and may be held on with 1 bolt. On some occasions, you will find a white cylindrical Capacitor instead. Replacing this should fix your problem.
Alternator Testing on a Portable Generator
If you had burning, smoke, electrical smells from the alternator, replaced the AVR/Capacitor for a second time or just wish to test your Alternator to be sure there are no other faults, our founder invented a new easier way to test all modern Portable Generators! No need for manufacturer’s expected readings with “The Beagley Alternator Testing Technique.”
We have created this training video to teach you the technique. It will guide you through testing and allow you to diagnose any other problems which might exist in the alternator.
For Capacitor (brushless) Alternators, please skip the brushes parts of the test.
If you have run these tests and want help to determine the results, please use the form below to tell one of our engineers the voltage results for:
Across the Brushes (if Brushes are fitted):
R1 & R2 :
L1 & L2 :
R1 & L1 :
If you believe you have a damaged alternator, feel free to get in touch using the option to start a repair ticket below, and we can guide you.
