Troubleshoot gen set

[chris piazza]

I got a 15kw onan in my 53C. While it always has been a little smokie It has always produce the correct voltage until the last time I went to use it this summer. I started it and while letting it warm up notice the output voltage had jumped from normal 220 to a little over 250v. Checked output with meter and found it to be correct. My thought is that the voltage regulator is bad? Is there a way to troubleshoot the voltage regulator? If so how do I do it? Any thoughts would be appreciated.

Chris
Superior Nights 53C

 

[captddis]

Check your RPM.

 

[Canuck Dennis]

There is a way to check the vr, it should be in the manual. requires a 6 volt ?? battery and some connections to the connections inside the electrical end, can be done yourself, if memory serves me right a new vr is approx. 1k+, but check rpm first, if you are over rpm then the hertz meter should also read high.

 

[chris piazza]

It didn't sound like it was running to fast but I guess its possible, I didn't check it. However I cant check it now (stored inside heated). What would make the RPM change?

 

[SKYCHENEY]

Chris,
If you do end up needing some parts for it, give me a call. I still have most of my 20kw and those may be the same parts.

 

[chris piazza]

Thanks Sky, I may poke around inside to see if anything jumps out as a clear problem. Still would like to know if there is a way to check the voltage regulator on a bench?

Chris

 

[Canuck Dennis]

The VR on my 20 was a totally sealed unit and non repairable, bit of a rip off ,even worse, when the new one showed up the connecting plugs did not match up, even though the part # 's were the same, more money to re wire with no explanation from the factory.

 

[SKYCHENEY]

Thanks Sky, I may poke around inside to see if anything jumps out as a clear problem. Still would like to know if there is a way to check the voltage regulator on a bench?

Chris

I have the service manual for my old Onan. I seem to remember seeing that procedure in there. I'll take a look and let you know.

 

[JLR]

Chris-if it is not the VR, you may want to check the governor. On mine, there is an arm that pivots with a spring and depending on the angle of the arm, the speed increases or decreases. There is also a little adjusting nut on the bottom of the arm. That nut (which is knurled in a way so that it can be turned by a screwdriver) adjusts the voltage as well. These items are mechanical and can vibrate loose over time.

 

[TopHattandTails]

I replaced my regulator board this summer for about $150 from Flight Systems in PA. Same group that works on the 12- point alarm panels... I had a bad potentiometer. New board was cheaper than repairing.

 

[Nonchalant1]

Check your RPM.

Also, when back in the water, check to see if it's producing 60 cycle current. Owners manual for 15KW Onan says RPM controls the cycles per second. Voltage is set by the controller board. Voltage can vary with RPM, but RPMs need to be set for correct A/C 60 cycles after correct voltage is being produced. You use pots on the control board to set the voltage first. If your board is shot, may need a new or used board.

 

[chris piazza]

I went up to the boat today to install a new cutting board in the bait station and to look into the generator problem. Can't troubleshoot a lot because I can't run the genny. The voltage regulator "appeared" to look OK. Nothing jumped out as far as broken PC board or blown resistor or bad wiring. I guess the experts may be right in keeping it simple and checking RPM first. The one picture is the governor arm and I assume that if this nut/bolt moved it would affect RPM?

Chris
Superior Nights 53C

 

[Avenger]

Changing the linkage between the pump and governor is not going to change RPM. The governor will just compensate for whatever you do to try to get back to the speed it's looking for. You need either a frequency meter or tach to measure actual RPM before you start making any adjustments.

 

[JLR]

Chris - I can't quite see from the picture but I think there is a spring on the right side of the horizontal arm that attaches to the vertical governor arm. Changing the angle of the horizontal arm where it hits that spring resulted in a change of rpm for me. Also, by turning the nut at the bottom of the arm changed the frequency as well. I do not know a lot about this stuff but it worked for me.

 

[chris piazza]

I have had that apart before when I changed the shut down solenoid, although that was a couple of years ago I guess it could have moved. Also how do I check the frequency and the RPM?

Chris

 

[Avenger]

Frequency would require a meter to plug into an outlet. It should be about 60Hz. Unloaded they'll probably suggest 61 or 62 depending on how accurate the governor is. RPM you would measure with either a photo or handheld tach on the crankshaft damper. Either one tells you the same thing, how fast the generator is turning.

 

[Canuck Dennis]

You could probably get away with using frequency alone as a set up, under load set at 60 or 61, if no load shows over 64 I would start getting a bit concerned, some electrical test meters will read hertz.

 

[chris piazza]

OK sounds like I will have to wait until April to go any further. I don't want to load the generator to check the frequency because I don't want to damage any electrical equipment on the boat. I guess check RPM first, get that right and than check frequency under no load? And yes that is a spring on the right side

Chris

 

[Avenger]

Frequency and RPM are directly connected. Measure either/or. The gen does not have to be loaded. Nominally they're 60 Hz and 1800RPM, but I would expect to see maybe 61 or 62 Hz no load because of the inaccuracies of mechanical governors. Do you have a manual?

 

[chris piazza]

I bought a new/updated manual 5-6 years ago but it only covers engine repair. I think I may have an original manual around someplace that does have minimal information on the electrical end.

Chris