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Voltage check

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healeyboz

healeyboz

Jedi Knight
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Checking the voltage off of the generator. If I check the two leads off of the back of the generator, should the volt output stay fairly constant? This thing seems to be spiking between somewhere around 10-19. Could I be having an issue with the regulator? Is there an easy way to check and see if the regulator is working properly?
 
Use the bugeye generator? Stabalizer should not be needed in any case.
 
I'm using the bugeye generator. It is supposedly rebuilt. Do you think this is a regulator issue?
 
Supose I would check the regulator or maybe even replace it, I hate working on them.

The manual explains all but I can not verify really.

Should think the generator output should be rather stable. Have autozone or such check it on their machine. tis free.
 
FYI, the voltage stabilizer in the Moss page is what powers the fuel gauge, it doesn't have anything to do with the generator output.

Is this voltage being measured with the generator and battery connected? If the battery is out of the picture, then yes, the voltage will be all over the place. Even with the battery connected, there will be some fluctuation since the regulator is rapidly turning the generator's field on and off to regulate.
 
If it's actually going to 19 volts and staying there long enough to measure on a multimeter, then that doesn't sound right. A voltmeter should be showing something around 14 volts, assuming the battery is connected. The regulator should be switching several times per second, much faster than your meter would show.

I think you are correct that Autozone would not be able to bench test the generator, since the regulator is a separate unit. Here's some info explaining the generator and regulator operation.
https://chicagolandmgclub.com/techtips/general/585.html

About the only means of testing the generator itself is to connect the armature and field windings together, and connecting a battery with the belt disconnected. If the generator runs as a motor, then it's working.
 
Thanks, the voltmeter that I have is digital and moves too quickly to accurately read. I am only able to see a few numbers every once in awhile. I assume that it is working correctly from what you have written.

Thanks
 
If you're getting that kind of voltage out of the generator, it's almost certainly OK. The real question is the regulator. When the voltage gets high, the regulator switches a resistor in series with the field coil, which reduces the voltage, but then that might be too low, so it switches the resistor out, and so on, back and forth. The cycle repeats with, ideally, the average voltage being 13-14 V.

Now, if you measure this with a digital voltmeter, the VM is sampling the voltage a few times per second, and the regulator is switching a few times per second, so the meter will more or less randomly indicate a high or low voltage. If this is what you're seeing, it's pretty much what I'd expect.

The real test is to measure the voltage at the battery. If it stays above about 12.5V (under normal conditions, I mean--might be a little lower if the electrical load is large and engine is slow) and never gets to be more than 14.5, you should be OK. If you start seeing values like 15V or more for longer than a second or two, you have a regulator problem.
 
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