I have a Lister Peter Hawkpower genset, 15kw 120/240 that doesnt produce any voltage at all. It used to be on a fire truck and worked great when it was on it, it was removed when we got rid of the truck and sat in the corner of the firehouse for a couple of years. I acquired it about a year ago, finally got it all set up to run, and it doesnt make any power at all. The generator head is a Marathon 334YC, which I cant find any info about it on the internet. It is a dual diode, dual capacitor setup. I have tested the diodes and they appear to be ok, not really sure though. Hopefully someone can shed some light on this for me.

 

I would suspect the grounding on the wireing, or the capacitors. If they are old they break down first in a circuit.

 

What do you have to energize the field? A battery? If it is the capacitance type ( from what you described) it could need a boost! Most generators, if left setting for awhile, can lose the charge. I've seen it before. Hook up 12 volts DC ( polarity isn't critical ) to the field windings and then fire it up again. Should get you going.

 

What he said.

 

What would be the best way to do that?

 

Its called flashing the field. You momentarily apply voltage to the field winding to establish a bit of residual magnetism.

A trick way of doing this is to plug in a corded drill, pull the trigger all the way then give the chuck a good spin by hand.

There is a slight residual magnetism in the drill and when you spin the chuck you spin the motor windings through the residual magnetic field. Whenever you move a conductor through a magnetic field you generate a voltage. So this slight voltage you just generated is enough to flash the generators field... sometimes!

 

If you can tell which wires go to the brushes, just put the 12 volts to them while it is shut off. the drill trick may work too!

 

It may just need to be connected to a battery in the same way it was on the truck. In the truck it may have had a low current disconnect, as you'd have in a car, to stop leaking voltage when the gen is off. This goes to the regulator and must be connected unless the gen is self exciting. When it was used in the firetruck it may have had a key switch with OFF ON START. The ON wires going to the regulator will have to be connected to produce current.

 

When it was in the truck it only had a connection from the starter to the truck batteries, and a ground from the generator to the truck frame. The off/run and start switch are mounted in a panel on top of the generator, and it had a remote start panel in the cab of the truck. This was all factory on this genset.

I tried the drill method and didnt get much. I have 2 volts ac across the 240 connections.

 

When you run it now are you leaving the starting battery connected to it while running? Or are you just jumping it to start? And are you still using the panel and key switch you mentioned to activate the starter or did those go with the truck?

I bet it's a wiring problem where you are not getting exciter current to the regulator and on to the genny.

 

The battery stays hooked to the starter. Still using all of the switches, they are built on to the generator, its a all in one deal.

 

Hmmm, sound like you still wound up with a nice genset!
I too tried to Google the generator end and only found this thread on DTR!
I am assuming it is a single phase, 120/240vac unit?

Your description sounds to me like a BRUSHLESS generator that has a pair of rotating diodes mounted to the rotor, and capacitors (or more) connected across a separate special stator winding which provides excitation to another corresponding winding on the rotor.
These special field windings, diodes and the capacitors all work together to excite and regulate the output voltage, all without using brushes.

If I am correct that yours IS a brushless model, that rotor winding is what the diode pair is wired to. They rectify the induced AC and provide DC for the rotating magnetic field. There are no brushes to "flash" the field with! And you can do serious damage by jumping DC into one of these units!

You say you checked the diodes, but did you make sure you lifted the attached wire off of each diode as you checked front/back resistance?
One diode could be blown wide open (infinite ohms, both directions) and the other one was showing good, fooling you, it still being connected to the bad one via the rotor/field winding.
ALso, make sure the capacitors are still being capacitors. No shorts, leakage etc..
Their push-on connections could be bad and causing no output.
If only one of your capacitors is open, that would seriously affect the voltage output, but I would guess that it would still put out much more than 2vac.

Another thing to check for, is any short ckt across the output wires of the genset. Make sure there is NOTHING shorted like chafed or pinched wiring, or other externally wired components like noise filters, capacitors, lamp ballasts, surge suppressors(MOV's), etc that could be shorted or burnt, keeping the magnetic field collapsed.

I first read this post at work today and was reminded of a wonderful GenSet Forum associated with Harry's Old Engines.. (I thought I had the URL bookmarked). It is a site with many excellent generator experts on Onan's, Kohlers, Generac, mil-surplus (Marathon!) etc. They are "THE" go-to folks to get any genset (old or new) troubleshot! If they don't have the answer, there is none to be had!
(after I post this, I'll find the URL and edit. )

EDIT: http://www.smokstak.com/forum/forumdisplay.php?f=6

Some time ago, I seem to remember reading somewhere on that site, a special flashing procedure used on a particularly lifeless brushless genset. It involved using several series wired 120v lightbulbs being used as current limiters to safely backfeed commercial AC power back into a running, but lifeless brushless genset. The object was to flash the dead, demagnetized rotor of a brushless generator head, but not blow it or yourself up trying to "flash" it the OLD way.

If you haven't fixed it, register there and throw out some queries about your Marathon generator... There are some really sharp people there...


Keith

 

I was also going to recommend asking around on Smokstak, I am also a member there.

Some of the guys there were factory technicians for some of the major manufactures.

Sign up and ask.
Jim

 

Searaching for a lift pump & an oil pan for a Yanmar 3cyl diesel genset. Anyone have a contact for used parts? thanks.