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Open Roads Forum  >  Tech Issues

 > 170VAC coming from my Onan generator

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SHRED

Encinitas, California

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Posted: 02/23/21 12:16pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

Hint: Use only FLINT PAPER on slip rings. Other materials embed abrasive particles in the copper wildly accelerating graphite brush deterioration. Brush contact to chassis ground resistance should not affect a 30 megohm reading. Disconnected from load the same is true for stator lead tests.


The Flight Systems tech pointed me to the brushes and rings for the ohm reading and voltage issues. That's why I am focused there. He said that the Onan voltage regulators do not like fluctuations and it very well could be damaged.

Anyway, I'm just passing along what he said.


1995 Lazy Daze 23.5' TK

dougrainer

Carrolton, Texas

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Posted: 02/23/21 12:30pm Link  |  Quote  |  Print  |  Notify Moderator

I never had brushes or rings cause an EXCESS of voltage. Usually low or no voltage. I HAVE had Voltage regulators fail on those older Onan's. Doug

PS. the ONLY thing that ever caused excess voltage was the Running speed of the genset. Never had the Voltage regulator cause extreme high voltage. Also, if your model Onan fails to produce 120, the genset shuts down.

SHRED

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Posted: 02/23/21 12:46pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

I never had brushes or rings cause an EXCESS of voltage. Usually low or no voltage. I HAVE had Voltage regulators fail on those older Onan's. Doug

PS. the ONLY thing that ever caused excess voltage was the Running speed of the genset. Never had the Voltage regulator cause extreme high voltage. Also, if your model Onan fails to produce 120, the genset shuts down.


I apologize for not being clearer.
In fairness the tech never claimed the brushes and rings caused the spike but rather most likely contributed to regulator damage (which has yet to be determined but likely).

bounder39zman

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Posted: 02/24/21 07:08pm Link  |  Quote  |  Print  |  Notify Moderator

This "M" spec Emerald runs at 1800 rpm and has an electronic voltage regulator. assuming governor speed is somewhat close to correct, then the high ac voltage is almost always caused by faulty voltage regulator. the field circuits are "stuck" in full field mode.
Flight Systems part number for the VR is model 305. Have installed dozens of these, with excellent results. better price and warranty than Onan part.

SHRED

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Posted: 02/24/21 07:20pm Link  |  Quote  |  Print  |  Notify Moderator

bounder39zman wrote:

This "M" spec Emerald runs at 1800 rpm and has an electronic voltage regulator. assuming governor speed is somewhat close to correct, then the high ac voltage is almost always caused by faulty voltage regulator. the field circuits are "stuck" in full field mode.
Flight Systems part number for the VR is model 305. Have installed dozens of these, with excellent results. better price and warranty than Onan part.


They are a great company.

The genset circuit breaker trips off. That was the original issue.
Do you think that the 170 VAC feed to the Automatic Transfer Switch damaged the ATS?
It's looking like that's the issue considering when I unhooked the ATS the breaker didn't trip.

I wanted to solve the high voltage issue first obviously before replacing the ATS if that's the issue.

Shore power works fine as does 12 VDC.

It is looking like a new regulator and new ATS might be what I need.

enblethen

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Posted: 02/24/21 07:43pm Link  |  Quote  |  Print  |  Notify Moderator

Doubt whether transfer switch was damaged.
I would be checking the converter and other electronic devices.


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dougrainer

Carrolton, Texas

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Posted: 02/25/21 07:07am Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

Doubt whether transfer switch was damaged.
I would be checking the converter and other electronic devices.


Bingo. IF the 170 made it thru the ATS, you WILL have fried components inside the RV. Since it appears either the ATS failed to close for the Genset or the Genset breaker tripped before getting to the ATS, either way, that protected you from interior component failure. Doug

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