gen set puts out 60 volts X 2

[mak]

I have a customer who's diesel gen set puts out 60 volts on each of two legs... the meter on the gen set says 120 volts and the switch on the gen set is pointing to the 240 volt out put. When I switch the switch to the 120 volt position, I get no volts... what should I be looking for?

[Hi yo silver]

A new generator??  Just kidding...couldn't resist.  Sounds like an "open leg" or phase.  Check for a blown fuse, broken terminal on a wire, and try turning off and resetting relevant circuit breakers.  How about it gurus, are we on the right track here?  Some of you have more experience than I do.
Dennis   

[Dallas]

Mike, It sounds like a pair of wires has come undone, and only half the windings are working.

Check to see if a reset switch has burnt out or a circuit breaker is FUBAR.

Since I don't know a lot about generators, my instinct would be to start at the receptacle and check continuity all the way back to the windings, on all three leads.(4 on 240V).

What kind of generator is it?

If nothing else, you could ask NCbob

Dallas

[DrivingMissLazy]

Sounds to me like the voltage regulator has gone south and the low output voltage is coming from the residual magnetism in the rotor field coils.
First thing try jumping 12 volts momentarily to the field. Output voltage should go up to 130 volts or so. If so, then the voltage regulator is defective. I would unhook the genset load before doing this so that you do not over-voltage anything in the coach.
Richard

[Stan]

Has your customer actually measured 60 volts on each leg or is that only a theory because of the 120 volts on the 240 volt meter? It makes a big difference  to guide him in troubleshooting. He may have one leg at 120 volts and one leg at zero or both legs at 60 volts. This would be two entirely different causes. As usual, we need more information to help.

[wcox]

If in fact he is getting 60 volts each leg, that will be an open ground or an ungrounded generator/transformer. That makes it an isolation generator/transformer. Have system professionally checked out soon. The erroneous voltage readings may be not having a reference point to read, missing ground/neutral.

        Wayne

[mak]

It is a diesel gen set 3600 RPM. It gets 60 volts from two legs.

[wcox]

Has the unit been changed, remounted new rubber feet. Anything changed recently?

[Stan]

If both legs are putting out 60 volts, then the likely reason is lack of enough field excitation. A 3600 RPM generator sounds like a cheaper model such as a Generac. If so, it may not have an electronic regulator, but just a bridge rectifier that feeds the AC output back to the field as DC.  If one diode in the bridge is open the field will only get half voltage. If it has a package electronic regulator, it would have to be tested to see if it is working properly. HTH.

[Hi yo silver]

One other thing; when trouble shooting problems such as this one, I have found that digital volt meters will drive you nuts, either by constantantly flucuating so fast that you can't read it, or by indicating voltage readings that are just "ghost" readings, picking up stray, trace voltage that isn't really representative of a circuit, i.e. you might read some odd voltage, but if you put the slightest load on it, such as a bulb, the voltage reading drops to nothing.  An analog meter won't mislead you that way.  Does that make sense?
Dennis   

[Ncbob]

Without a brand name I'm normally reluctant to get involved in these discussions but I will venture into it for the sheer adventure...it's been a dull day so far.

Any time a generator voltage is questioned the first thing to check is the FREQUENCY!  No matter what the voltage reads if the frequency (read engine speed) isn't correct the voltage will never be correct.  If the voltage, whatever it is, reads 60-61 Hz it's a connection or regulator problem.  Have we taken for fact that the leads from the stator are connected properly or double checked them?  12 lead generators usually have at least 2 sets of leads off on the side not connected to anything but each other. Double check the connection diagram for proper connection.

That being done check the Hz. and voltage.  A meter might read 60 volts but it's not an acceptable voltage.

Could it be that this is one of those new generators wherein the engine speed increases with  the applied load? Honda offers a few of these and there are quite a number in buses.  Honestly...more information would be a big help.

NCbob