How to Test a Brushless Generator

Updated 1 week ago by Juan Velez

This covers the following Champion Power Equipment models: All 1200-1800W Generators.

Read instructions carefully and completely before performing service.

Diagnostic Testing of the AC Voltage Electrical System

By using a common multimeter (VOM - Volts Ohms Meter) for the Volts-Ohms measurements, you can do a diagnostic on the AC output of the generator.

Test 1A

Remove the yellow end cover (vented cover over generator) and unplug the 4-wire plug with a red and black wire (AV voltage to outlets) and two yellow or orange wires coming the from exciter winding within the stator. Using the meter set to AC, connect each probe (no direction is required) on the two orange/yellow wires and obtain the reading. This test is performed with the engine running. A normal reading will be between 6.2 AC volts + or - 5%.

Test 1B

Reconnect the plug-in connection and start the generator. Setting the meter to AC voltage, place your test probes on each of the yellow or orange wires, and the reading should be just about 150 volts AC. If this test is to specifications, then the condenser is functioning normally. You will not have to test any further or disassemble the panel cover. Your panel voltage should be at or close to normal (115V-125V AC).

Test 2

This test involves the removal of the four panel bolts and relaxing the panel assembly away from the chassis. On the backside of the panel is a black dust cover that is held on by two Phillips screws. Upon removal of the screws, you will move the dust cover away from the panel and see a small black box (condenser or capacitor) that the yellow or orange wires are attached to. Remove any of the two connections and do a microfarad test across the terminals on the condenser. This test will set your meter to an icon that looks like a "uF." Usually, a mode position of the Ohms scale is a "horseshow" icon. The result should be about 7 uF (microfarads) + or - replaced.

Test 3

With the generator running, you need to set your meter to AC and then place one probe on each blade terminal at the AC outlet on the front panel. You should have a reading between 115 and 125 volts AC. Adjust this range with the governor screw about in reference to the recoil housing of the start rope. Due to the condenser style excitement used on this model generator, you will noticed a somewhat unstable view of the AC voltmeter to give a solid hold at any particular setting. Turn it until a happy medium of this voltage range in determined. Of course 120 VAC is the most desirable medium. Do not be disappointed if your setting is only close to this number and any slight movement changes the setting. A little trial and error will work with your setting.

Static Testing of the Stator and Rotor

Stator Testing

With the nylon plug disconnected under the yellow cover, an Ohms test can also be performed on the stator. Using the probes of the VOM and touching them to the ends of the yellow or orange wires, you will get a result of about 3.8 Ohms + or .2 Ohms. Outside of this range will indicate a failure of the stators exciter field winding.

Now you can test the red and black leads at the nylon plug on the stator. This test should give a positive result of 1.5 Ohms + or - .2 Ohms. Outside of this range will indicate a failure of the main winding of the stator.

Rotor Testing

You will note that the ends of the field winding wires include a resistor between them. If the resistor is tested in place, the reading will be about 8.7 Ohms + or - 5%. If the resistor is removed, then the test will show about 10 Ohms when the ends are tested of the field winding wires. Any numbers outside of the 5% of this test will indicate failure of the rotor, and a replacement will be necessary.

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