170VAC coming from my Onan generator

Under some circumstances digital volt meters can read "ghost voltage". This typically occurs when there is no voltage at all on the probes but there is voltage in nearby wires. Ghost voltage is usually unreasonably high.

Best solution is to use a very low wattage light bulb across the points you want to test and the meter leads across that. If the high voltage is real it may blow the bulb so be careful !

As Gary said early on, find a meter that reads HZ. This is used to adjust engine speed to adjust HZ and voltage. Voltage should be unloaded around 124-128 volts AC.
Manual

Flight System Has after market good quality replacement parts.

time2roll wrote:

SHRED wrote:
I didn't see "regulator" in there.

Might interchange the word governor since it regulates engine speed.

1. Engine governor incorrectly
adjusted

Yes get it in to a pro for best results.

I was trying to avoid that in that they want about $550 just to diagnose the problem at my local Onan/Cummings dealer.

Ugh.

SHRED wrote:
I didn't see "regulator" in there.

Might interchange the word governor since it regulates engine speed.

1. Engine governor incorrectly
adjusted

Yes get it in to a pro for best results.

dougrainer wrote:
AC Output
Voltage Too Low
Or Too High
Noisy Generator
Possible Cause
1. Open circuit breaker
2. Open circuit between brush
block an CR4 rectifier
3. Brushes stuck in holder or
not making good contact with
slip rings
4. Defective CR4 bridge
rectifier
5. Open, grounded, or short
circuit in rotor, stator, or
transformer
1. Engine governor incorrectly
adjusted
'2. Open diode in CR4 bridge
rectifier
*3. Brushes worn or not making
good contact with slip
rings
4. If generator frequency is
within specified limits but
voltage is incorrect,
transformer is incorrectly
connected or defective.
'5. Open, grounded, or short
circuit in rotor, stator,
or transformer
'causes low AC output voltage
1. Loose brush holder
2. Worn generator end bearing
3. Rotor and stator rubbing
together due to: a) varnish
lumps, orb) rotor
misaligned with crankshaft
Corrective Action
1. Locate cause of overload
and correct as required.
Reset breaker
2. Check for continuity and
correct if circuit is open
3. Release brushes if jammed
in holder. Clean slip
rings if dirty.
4. Test rectifier and replace
if defective
5. Test each component for
open, grounded, or shorted
windings and replace if
defective.
1.
2.
3.
$.
5.
Refer to Governor
section
Test CR4 rectifier and
replace if defective
Check length of brushes
and replace if worn
excessively. Clean or
replace slip rings.
Adjust tap connections on
transformer secondary
windings to obtain correct
voltage. Replace
transformer if voltage cannot
be corrected with adjustments.
Test each component for
open, grounded, or shorted
windings and replace if
defective.

I didn't see "regulator" in there.

I'm getting to the point where professionals need to look at this mess I think.

I did unhook the ATSwitch and the breaker on the genset didn't trip off which was my original symptom.
Now I'm thinking the high voltage may have damaged the ATS.

AC Output
Voltage Too Low
Or Too High
Noisy Generator
Possible Cause
1. Open circuit breaker
2. Open circuit between brush
block an CR4 rectifier
3. Brushes stuck in holder or
not making good contact with
slip rings
4. Defective CR4 bridge
rectifier
5. Open, grounded, or short
circuit in rotor, stator, or
transformer
1. Engine governor incorrectly
adjusted
'2. Open diode in CR4 bridge
rectifier
*3. Brushes worn or not making
good contact with slip
rings
4. If generator frequency is
within specified limits but
voltage is incorrect,
transformer is incorrectly
connected or defective.
'5. Open, grounded, or short
circuit in rotor, stator,
or transformer
'causes low AC output voltage
1. Loose brush holder
2. Worn generator end bearing
3. Rotor and stator rubbing
together due to: a) varnish
lumps, orb) rotor
misaligned with crankshaft
Corrective Action
1. Locate cause of overload
and correct as required.
Reset breaker
2. Check for continuity and
correct if circuit is open
3. Release brushes if jammed
in holder. Clean slip
rings if dirty.
4. Test rectifier and replace
if defective
5. Test each component for
open, grounded, or shorted
windings and replace if
defective.
1.
2.
3.
$.
5.
Refer to Governor
section
Test CR4 rectifier and
replace if defective
Check length of brushes
and replace if worn
excessively. Clean or
replace slip rings.
Adjust tap connections on
transformer secondary
windings to obtain correct
voltage. Replace
transformer if voltage cannot
be corrected with adjustments.
Test each component for
open, grounded, or shorted
windings and replace if
defective.

MEXICOWANDERER wrote:
You need to seek and record the MODEL and the SERIAL NUMBER of your generator then post it. Some generators are volts per Hertz (speed sensitive)

And DO NOT TRUST a critical finding like this to a single measuring instrument.

MODEL: 4BGEFA26100M

SERIAL: D953355775

You need to seek and record the MODEL and the SERIAL NUMBER of your generator then post it. Some generators are volts per Hertz (speed sensitive)

And DO NOT TRUST a critical finding like this to a single measuring instrument.

Check the batteries and verify your meter is reading correctly by checking voltage from home source.
Just saying cause I had this happen to me once.

Gjac wrote:
Does your genset seem like it is running at a higher rpm than normal? You can buy cheap HZ meter plug it into your 120 v socket and adjust the speed to read the correct HZ at the proper rpm.

Look and see what the output voltage is supposed to be. At that voltage it is also running at 60 HZ, this has to do with the building of the generator.

So using a decent volt meter will do.

If there is an adjustment on the governor I would try slowing the engine down while watching the output voltage, setting it at or a whisker over.