# Old Haverhill Generator Produces Low Voltage Problem



## phower (Mar 3, 2019)

Hi - I have an old Haverhill Generator Set run by a Honda GX110 and with a Barrett Alternator. With a light load applied in one outlet (50w bulb) it barely lights, and on measuring voltage at another outlet at the same time, it measures 80 volts. Should be 240v. I don't have the means of measuring HZ. I have checked the 2 Bridge Rectifiers and they are operating correctly. The engine is at max revs when producing the 80v, and lower volts at lower revs Is there any relevance to 80v being a third of 240? I can't take off any plate to see the back end of the Alternator as there isn't one - all cables terminate to various points inside a metal box on top of the alternator. All connections seem ok - there is a part in there that I'm unsure as to its function, it looks like a rheostat of some sort (tubular with coil of fine wire round it and cables either end, 2/3rds the way along the tube is a connection clamped to it that looks like you could move it along if you undo the clamp screw. Not something you would fiddle with, its too buried in the metal housing but does look like you would vary voltage in some way if you wanted to.


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## tabora (Sep 6, 2018)

If it has not been run for a long time, it may just need some time... I have an Onan that I purchased in 2001 but didn't actually install until 2018. I also had 80V output at first. After running it for a couple of hours, it's now fine. Perhaps the brushes just need some time to get acquainted with the slip rings, or ultimately may need replacing.

What is the Model? I only saw parts online for a B105C.


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## RedOctobyr (Aug 8, 2018)

It this one of those scenarios where field-flashing the generator might help? Like with a corded drill plugged into the generator, then you turn the drill by hand?


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## phower (Mar 3, 2019)

tabora said:


> If it has not been run for a long time, it may just need some time... I have an Onan that I purchased in 2001 but didn't actually install until 2018. I also had 80V output at first. After running it for a couple of hours, it's now fine. Perhaps the brushes just need some time to get acquainted with the slip rings, or ultimately may need replacing.
> 
> What is the Model? I only saw parts online for a B105C.


Thanks - I'll give that a try. Not sure of the model, it doesnt say but does have a plate with serial numbers of the unit, the alternator and the engine which all match.


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## phower (Mar 3, 2019)

RedOctobyr said:


> It this one of those scenarios where field-flashing the generator might help? Like with a corded drill plugged into the generator, then you turn the drill by hand?



It may well have been a help - I first reviewed the web and came across that idea and tried it. At first I had nothing but then tried increasing the gen revs and thats when I found the 80 volts. It may well have been the flashing that started it off though?


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## phower (Mar 3, 2019)

By way of feedback I tried all of the above to no avail - any more ideas anyone?


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## Osviur (Sep 7, 2015)

Hi Phower,

With the gen running, check the rectifier voltage output, the one connected to the adjustable resistor. If DC present, maintain one test probe in the negative rect output and check for voltage at the resistor black cable. This seems to be the DC power for excitation. If no voltage, check for rusted contacts in the adjustable resistor.

The 80 volts can be generated with the magnetic remanence in the rotor in absence of the external excitation, Better, if accesible, check for voltage in the generator brushes. If voltage (30-90VDC) present and no AC output, check for continuity between brushes (input cables disc): 15- 30 Ohms.

Hope this help. Good luck!


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