170VAC coming from my Onan generator

[SHRED]

It's a 1995 4000 BGE.

I posted earlier but wanted to focus in on this problem.

I tested the lead coming into the breaker switch and it was a consistent 170 VAC.

What should I check next and how?
Regulator?

Thanks

[larry_cad]

MEXICOWANDERER wrote:
Your ohmmeter is playing Three Card Monte with you. The slip ring leads are encased in a nylon sheath then varnish dipped and baked. They would have to touch each other in order to slow low resistance.

Connect two test leads across 12 volts. Connect your ohm meter to generator AC output. Be careful. Start generator. Do you see reasonably steady voltage?

Connect one test lead in series with the probe through the ammeter 10 amperes setting. Be sure the meter is set to amps and the lead is plugged into the right hole.

Any violation of integrity with the windings in the spool or slip lead connection will show up when the rotor is revolving. Engine running. Wild variances will scramble the meter numbers. Drag the points of the probes, wear short sleeves and move slowly when the engine is running.

I'd tell you how to test the voltage regulator with a battery and a VARIAC, but...

Do you really want him to "Connect two test leads across 12 volts"??

Do you really want him to "Connect your ohm meter to generator AC output"??

I understand what you are really trying to say, but someone who would do exactly what you tell them to do would have a small disaster on their hands along the lines of melted and burnt clip leads, and a blown up "multimeter".

[Gjac]

SHRED wrote:

Gjac wrote:
Shred, how are you making out with your Genset?

I have an appointment to take it in to a recommended shop here in the San Diego area. Quality RV.

Good luck to you, hope you get it resolved. When my voltage was high it turned out to be the electronic governor board, but I could hear the RPMS being high and the hertz was off also, and Flight Systems sold me a new board and it work fine after that.

[SHRED]

Gjac wrote:
Shred, how are you making out with your Genset?

I have an appointment to take it in to a recommended shop here in the San Diego area. Quality RV.

[MEXICOWANDERER]

Your ohmmeter is playing Three Card Monte with you. The slip ring leads are encased in a nylon sheath then varnish dipped and baked. They would have to touch each other in order to slow low resistance.

Connect two test leads across 12 volts. Connect your ohm meter to generator AC output. Be careful. Start generator. Do you see reasonably steady voltage?

Connect one test lead in series with the probe through the ammeter 10 amperes setting. Be sure the meter is set to amps and the lead is plugged into the right hole.

Any violation of integrity with the windings in the spool or slip lead connection will show up when the rotor is revolving. Engine running. Wild variances will scramble the meter numbers. Drag the points of the probes, wear short sleeves and move slowly when the engine is running.

I'd tell you how to test the voltage regulator with a battery and a VARIAC, but...

[Gjac]

Shred, how are you making out with your Genset?

[SHRED]

Update:

Replaced brushes and springs.
Shined the rings.
That brought my stationary ohm reading into tolerance on the 9/10 pins at 25 ohms.

Problem is during spinning the ohms flucuate from 0.00 to OL at those same pins.
I think I have a short in the rotor.

[dougrainer]

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

[enblethen]

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

[SHRED]

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.

[bounder39zman]

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]

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).

[dougrainer]

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]

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.

[SHRED]

enblethen wrote:
Fight Systems sends a tool to clean slip rings

I ordered it.
It'll be here Friday.