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10Kw Powertech speed/output fluctuation -- under load

April 08, 2013, 07:21:50 pm

As I continue with my restoration and upgrades every weekend -- I run the Gen-set with the boost switch on every 3 weeks or so -- for about 2 hours.

The last couple of times a new condition has cropped up. When first firing it up it purrs just fine. I then turn the Inverter on and the master switch. The voltage meter above the door shows a steady 110 volt output.

But then when I put a load on it with the forward roof A/C unit, the gen-set starts a slight "hunt" -- with a pitch change due to speed change, and the volt meter needle varies from 110 to 115 volts with speed change.

If I then walk back and turn on the rear A/C unit to increase the load, the effect is more pronounced ( the frequency of the hunting increases).

If I turn off both A/C units, the Set runs steady and fine again.

Any idea's of where to look?

I'm thinking one possibility is that the main fuel feed line is starting to suck air through the hose wall ( I replaced the entire length of the one for the CAT, but not this one), but the inadequate quality of fuel that would result is not affecting the running in a no-load condition.

All other electrical aspects (12 VDC) and A.C.  (like televisions, micro-wave, etc.) run just fine.

All advice and comments are appreciated. This is exactly the kind of shaking out I'm hoping to complete before doing the full-timing thing in a few months.

All the best,

Michael

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #1 – April 08, 2013, 07:43:42 pm

I have the same problem. I took the advice of others here a took off the factory fuel line and took a five gallon can of diesel fuel with a hose in it. I loaded up the generator and it ran fine for three hours. I still have to replace the factory fuel hose, just need some spring weather to do it. Mark

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #2 – April 08, 2013, 07:45:58 pm

If it were my generator acting up as you describe, the very first thing would be to get a reliable AC Volt meter, and adjust your voltage to 120-122 volts no load, NOT 110 Volts,  then check/replace air filter & fuel filter, then load both a/c units and see how it goes, if still unstable, use a seperate 5 gal can of good diesel fuel, inset the fuel pickup hose from the fuel pump into it and get engine primed and running and add the load again.
Might be good, if not, let me know what generator your using, Isuzu or Kubota engine ?
if by chance you have a gasous generator, you need to start adjusting sensitivity & speed, then hope alot.

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #3 – April 08, 2013, 08:36:57 pm

Dave,

It's a Kubota -- unless I'm mistaken.

By the way, where is the voltage adjustment performed?

Thanks for the comments. I do suspect the fuel-line. I already have a new fuel and oil filter -- and was planning on servicing it. When I acquired the Coach and pulled the dipstick -- the oil was a clear honey color and it appeared had barely been run after a oil change. It has about 760 hours on the totalizing meter.

Michael

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #4 – April 08, 2013, 09:13:01 pm

We recently replaced the fuel lines for our 1997 Kubota 10KW Powertech. Our generator ran fine at the beginning of a trip and then would not keep running. It appeared that the fuel lines were sucking air. We went to FOT for diagnosis and repair. They verified that the fuel lines were bad. They also showed me the failing lines for the Cummins engine. They replaced all fuel lines. Both engines have run fine since the fuel lines were replaced.

It appears that a lot of folk with coaches of vintage 1995-1999 are replacing fuel lines.

Your generator is almost new. Our generator shows about 3500 hours on the clock. The Cummins shows about 2200 hours.

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #5 – April 08, 2013, 09:16:55 pm

Would assume it is in the control box behind the hour meter etc, Unless you have a good volt meter, leave it alone, Lots of things get screwed up worse with poor meters and electricians than God with lightening strikes.

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Re: 10Kw Powertech speed/output fluctuation -- under load

Reply #6 – April 10, 2013, 08:36:49 am

I'm not sure that fuel lines are your problem.
I had FOT replace my generator lines a year or so ago.
(Altho the fuel line into a bucket of diesel might tell).

I too have fluctionations in output when I run both A/Cs (only when running from the generator). The forward one runs just fine but when I add the rear the output voltage becomes erratic. One of these days I'll swap capacitors on the A/Cs and see if that changes anything.

We run North in the summer. Last year I only ran both A/Cs about 3 times. It was 87 in San Antonio yesterday--time to head out again.

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