# Tow Behind, Trailer Mounted 7kw Generator



## Jack D (Dec 6, 2012)

Knowing my Kawasaki 3000 kw genset is marginal as a home back-up (it barely runs the well pump), I began searching for something else. I was also needing a Winter project and wanting to save money.

This project, assuming I can make this genset work, will be to build a trailer to mount it on to tow it with my garden tractor around the property as needed. I will likely convert it to propane only or perhaps duel fuel (gasoling and propane). I will also convert the output to 120V/240V (it is 120V only as it sits).

I found this old Kohler (7CM21) 7kw genset salvaged from a motor home. Seller stated that in runs, but only when the "start button" is held in start position. He also stated that it doesn't generate any output and suspected the regulator was out. That was a red flag to me, but the price was right ($140) so I bought it, hoping that I could make it work without buying a new regulator (~$350). It came with a service manual and schematics.

I got it home and on the bench. After looking it over closely, I started the engine using starting fluid (no fuel pump or fuel tank, yet). It fired right up. Next I started checking circuits continuity and current flow and most looked good. There was some corrosion at some electrical connectors and the circuit breakers as well as the rocker start/stop switch are shot. I cleaned the slip rings and corroded connectors. I've ordered a new fuel pump and rocker switch.


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## rhenning (Jul 23, 2011)

I have something similar. It is made from an old CC frame with Generac tractor mount Generator and a 6.5 HP HF engine for power. Nice when I feel like using electric things out in the yard. Roger


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## Jack D (Dec 6, 2012)

rhenning said:


> I have something similar. It is made from an old CC frame with Generac tractor mount Generator and a 6.5 HP HF engine for power. Nice when I feel like using electric things out in the yard. Roger


Nice! Similar to what I have in mind.

The rocker switch came in yesterday. Still waiting for the electric fuel pump.


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## Jack D (Dec 6, 2012)

Finally got the fuel pump installed. Started right up and ran nice and smooth, but only if I held the start button. Checking the oputput of the generator, I only get 55VAC.....about half what it should be. Checking with my brother, a 20 year Navy electrician and retired factory electrician (millright), he said it most likely has an open field winding. Another possibility is stuck brushes....and I will check that, but have my doubts. 

Assuming it's not stuck brushes...Options are to look for another generator of same manufacturer that needs an engine and put the two together into a working unit. Or to have this one rewound...probably too expensive. Or to part it out and sell the parts.

What would you do?


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## Jack D (Dec 6, 2012)

Slept on the problem last night and at some point, it dawned on me that I have checked continuity on all of the windings and they are OK. My problem can't be windings. Today I look for bad connections...including stuck brushes. I'm going to get this thing working, yet.


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## Jack D (Dec 6, 2012)

Decided to take the regulator apart, since I was convinced it was bad....and it was. There was a hole burned clear through the back and when I took the bottom plate off there was a big melted spot inside. Then I checked continuity and short to ground on the flash windings. Shorted. Generator portion is shot.....Dang!

Now I'm looking at an Onan 6.5NHE 1?/ 251004 (Barely legible, could be wrong) Listed as a 4.0 kw but plainly marked as a 6.5 kw. Looking at the probable schematic, it appears that this genset can be re-wired for 240V, but not sure. Still researching. I need a schematic for one similar that is wired for 240V. This one (if I have the right schematic) has a transformer that confuses me.

My 7CM21 will be parted out.....unless someone wants the complete engine.


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## 89yt12 (Sep 20, 2010)

sounds like you been having alot of fun


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