Onan 6.5 NH voltage high and low.

[CapnDirk]

Before I have to join another forum for an answer I thought I'd bounce this off our people and see if I get lucky.


After taking care of a few problems including way to big plug gap and a missing fuel pump the engine is running well.  My next step was to check voltage.  The ouput of the generator wired for 240 was 165V AC not good of course but while doing this I happened to see through the vent opening on the electric choke to see the inside of the choke glowing red.  I shut it down and got my volt meter.  To my horror, the line to the choke showed 48V DC!  I shut it down immediately, and hope I didn't toast the new fuel pump.


So if anybody knows where to start looking (would like to take care of the 12V issue first as that will damage components)  I would appreciate the input.

[tmsnyder]

I'm confused, what do you mean 'wired for 240'?  Isn't it 120V like every other Onan 6.5 kw rv generator out there?


Mine is similar to yours except it's 120V,and I remember from adjusting it per the service manual that with no load these run a little faster than 60hz and at a somewhat elevated voltage.  Once a load is applied the motor speed and voltage come down towards 60hz 120V.  And there's a pretty generous window of both where things will run just fine on that power. I set mine to run so that when the roof A/C is running the voltage is 120 and the speed is 60 hz.


If you are seeing 165V AC on the output, then I would check the hz of the generator, it sounds like you have the govenor set too high.  This would give you high hz and high voltage expecially with no load on the generator.


What's the hz reading?  Gotta get that right first for the voltage regulator to be able to do its job.

[CapnDirk]

TM:


This can be wired either way.  120 or 240.  There are two 30 amp breakers on it for each leg.


I've subsequently checked the diode and two resistors and the low volt output is correct  I have 12.2 at the fuel pump and coil..  The choke is wired differently to be at about 30 volt.  This is for the heater coil that's in it.  Trust me when I say don't lean on the choke!   

[CapnDirk]

Well, disaster has struck apparently.  I've had it running many times sorting things out in the carb, ignition, fuel, and 12V systems and have been making steady progress.  However, while running it trying to figure out the AC voltage issue, the generator body itself started spewing white smoke with that electrical smell.  Nothing has changed, and given the numerous times I've run it I can't fathom why the generator windings or whatever would toast.


Anyone have any ideas?  Output on the two AC wires was 153V

[Rickf1985]

It sounds like the voltage regulator went out but if there was that much smoke then it sounds like it took the windings with it. Was there any load on it at the time? No matter what you will be doing a tear down to see what smoked so that will pretty much give you an idea of what was going on in there.

[CapnDirk]

Yea, figured that.  I'm not sure as to where the voltage regulator is.  The manual says that the voltage regulator did not start until spec R and this is a spec P

[Rickf1985]

My generator expertise is on the military sets, Dave is the RV genny guy. It's funny but you would think that being a military set it would be indestructible right? The generator portion is but the regulators on those are as fragile as can be and go out a lot. AND they are Onan's.