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Generator Voltage Problem

May 31, 2011, 06:04:32 pm

I have the 8 kw PowerTech diesel generator.  Last week after start the voltage was high about 135 to 150 depending on load.  Manual recommends to replace the AVR automatic voltage regulator.  I was able to get the voltage into a normal range of 120 volts by cycling the generator breakers off and back on.  Voltage was fine for 2 hours and okay after a couple of starts.  Yesterday it was high again after start.  Spoke to PowerTech tech service who thinks the AVR needs replacing, but something else might be causing the problem as well.  Haven't found any loose or corroded connections.  Before I order a new AVR would like to check the brushes and if it needs them order both at the same time.  Has anyone either checked or replaced the brushes?  It appears that the brushes can be replaced through a cover plate on the end of the generator.  Can anyone confirm that?  2100 hours on the meter.  Thanks.

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Re: Generator Voltage Problem

Reply #1 – June 01, 2011, 01:11:35 pm

I should have added that I removed the 2 screws that appeared to be fasteners for the brush holder, but that it didn't move.  I didn't put much pressure on it.  Power Tech has not returned my call today.  Seems no one has done this. 

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Re: Generator Voltage Problem

Reply #2 – June 05, 2011, 08:16:05 am

Hi Jerry,

I have no idea on how to do this with a PowerTech, but with my Onan the service manual shows using a piece of wire with a mark, fitted into an opening, to establish how much of the brushes is left. If the mark is not visible when the wire is inserted, the brushes are worn and need to be replaced. Did not remove any fasteners to do this check - only an inspection cover. I found an online source of brushes for $7.95 - and although mine show about 40% left, am going to order a set to keep on hand.

My generator shows just under 2000 hours. Don't know if the brushes were replaced before this. Manual says check them every 500 hours. Am finding a service manual and a parts manual very valuable resources.

Hope this helps.
Steve

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Re: Generator Voltage Problem

Reply #3 – June 05, 2011, 03:13:25 pm

Steve,

Thanks for the reply and advice.  I made another attempt at removing the brushes and was successful, they were just stuck in place and required some force to break the holder loose.  If they are the original brushes they should last at least another 2000 hrs.  Also checked the end bearing and it seems ok, at least the inner race is not turning on the shaft and the outer race is not turning in the housing.  Ordered a new voltage regulator from Power Tech on Friday.  The online order form had a place for a discount code, so I emailed them and asked for one which reduced the cost from $215 to $197.75.  Just waiting for the regulator to show up. 

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Re: Generator Voltage Problem

Reply #4 – June 10, 2011, 03:08:25 pm

The new automatic voltage regulator AVR has been installed and the voltage is correct after 2 starts and an hour of operation.  Replacing it was rather simple, unplug the 6 wire connector, remove 2 screws holding the regulator place, install the new one, and replug the connector.  I didn't try to tweak the voltage with the tiny adjustment screw as it was 119 at no load and 116 +/- with 2 AC units running.  Steady reading with no load, varies 2 or 3 volts with a load.  Frequency okay at 61 +/- a little. The microwave used to make a buzzing sound for about 5 seconds after the generator came on line with the old AVR, now it doesn't do that.  A bit nerve wracking working on an expensive piece of equipment  and not real sure about what to do. 

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Re: Generator Voltage Problem

Reply #5 – June 10, 2011, 10:18:32 pm

Jerry ;
    Make sure the regulator is properly fastened and the heat sinks do not ground against anything as they are hot electrically when the gen is operating.

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Re: Generator Voltage Problem

Reply #6 – June 10, 2011, 11:11:19 pm

Gary,

Thanks, but we must have  different generators.  My AVR does not have heat sinks, it's just a potted deal in a shallow plastic case.  Looks like this.  Power Technology Southeast Inc - Voltage Regulator VR 2.1 (Brush)

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Re: Generator Voltage Problem

Reply #7 – June 10, 2011, 11:37:07 pm

Neeevermind

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