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My Onan 2.8KV series G, shuts down after start button

Customer Question
Hi, My Onan 2.8KV...

Hi, My Onan 2.8KV series G,
shuts down after start button released.Checking voltage on VR connector, it runs at half volts and frequency:
Output on pins 2-3 : 60V ~25-30Hz
Pins 9-10, about 20V at the same 25-30Hz frequency
Resistance when disconnect from VR on 9-12 about 20 OhmNot sure if this is faulty VR, slip rings , rotor or something else.

Mechanic's Assistant: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?

Yes

Mechanic's Assistant: Do you plan on doing the work yourself?

So far

Mechanic's Assistant: Anything else we should know to help you best?

Its starts but does not keep running after start is released due to low voltage on output.

Submitted: 6 months ago.Category: Small Engine
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Customer reply replied 6 months ago
correction: resistance on 9-10 is 20 Omh ( disconnected)
Field Flash on Pin 7 is 12.2V
Answered in 3 hours by:
12/22/2017
Technician: Hank F., Technician replied 6 months ago
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15,897
Experience: Certified on Onan and Generac generators
Verified

Hello, my name is ***** ***** I am going to assist you with this.

What is the full model number of the genset?

How long has it been since this unit was run regularly?

Has any work been done to it recently?

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Customer reply replied 6 months ago
Hi Hank.
>What is the full model number of the genset?
2.8KV FA11574GHow long has it been since this unit was run regularly?
Was using it for the last month. it has stopped working 3 days ago.
It was probably not used too much before, only 300hrs on it.>Has any work been done to it recently?
Oil change few weeks ago, was exercising it for couple of weeks with B12,
it started to run much quieter and more stable, 50+% load
then suddenly stopped. Before stop voltage etc were OK.Changed oil again since then ( was pretty dark after about 10 hrs!), checked carb float - clean, checked spark, good.
Made sure it starts correctly, while start button is pressed. it sounds as it works,
exhaust is ok, surging when choke.Checked voltage levels and found issues as described in initial message.
It is still below coach, so amount of work I can do is limited.
Imho almost exact 50% loss of frequency and voltage on both input and output of regulator is very suspicious to be coincidence.
Technician: Hank F., Technician replied 6 months ago

If you press and hold the start button to keep it running, does it seem to be running normally? Rough? Fast? Slow?

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Customer reply replied 6 months ago
Seems normal
Technician: Hank F., Technician replied 6 months ago

Connect your meter to the actual output leads of the genset, and retest the voltage and frequency.

What readings do you get there?

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Customer reply replied 6 months ago
Not sure what you mean by this, Pins 2/3 of mating VR connecter goe to output. It is 60V and 25 to 30Hz.
Technician: Hank F., Technician replied 6 months ago

Pins 2 and 3 of the VR are located after a splice.

I need the voltage and frequency checked before the splice. The splice could be bad, because the readings you are getting are not backing up what you say is happening.

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Customer reply replied 6 months ago
Looking at news groups, will it be advisable to try?With the regulator still unplugged, you *could* check the windings, control board, etc by jumping 18v dc to pins 9 and 10 in the wiring harness plug (which connect to the brushes) while you have the set running - this should give you a nominal 120v output, or close enough to switch the control board to run mode - then measure ac voltage between pins 2 and 3 (should be output voltage, 120v +/-), and measure the exciter winding output between pins 11 and 12 (should be about 85% of output voltage).
Technician: Hank F., Technician replied 6 months ago

18V probably wouldn't give you 120 volts.

But the big problem right now is not the voltage - it is the frequency.

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