Generator head replacement

Topic: Generator head replacement (Read 3399 times) previous topic - next topic

Generator head replacement

February 10, 2023, 11:16:05 pm

Finally getting around the tearing down the generator. All the testing says the windings are shot. Powertech has no parts any longer. Marathon is trying to match this one, however mine is an Isuzu, mat not be the same flywheel pattern as a Kubota. We'll see.

Re: Generator head replacement

Reply #1 – February 10, 2023, 11:31:12 pm

What about getting the part that is haywire rewound.

Re: Generator head replacement

Reply #2 – February 10, 2023, 11:46:58 pm

Quote from: oldguy – February 10, 2023, 11:31:12 pm

What about getting the part that is haywire rewound.

that may be possible, however some parts are not rebuildable. A new complete replacement placement head from marathon Is 3K. When talking rewinding, starts at around 1400.00 and goes up
From there, then add freight. Got to
Keep in mind this machine is 25 years old. So you get the one part repaired, how long before the next part craps out.

Re: Generator head replacement

Reply #3 – February 11, 2023, 07:59:27 am

Bruce, have you checked used prices at some of these salvage yards? Of course, it will depend on where they are located, but there are many Foretravels out there sitting in these yards! I know there are not many left still in business, but we had an electric shop in Lebanon, TN that rebuilt just about anything out there. These specialty companies are about gone from the landscape now, but that is another choice if cost is in line with repairs!

Re: Generator head replacement

Reply #4 – February 11, 2023, 08:50:08 am

I have replaced three generator heads using new ones from Central Georgia Generator. Generator Accessories – Gas Generators | Central Georgia Generators
Tom down there is excellent and they are fair and knowledgeable. I have no connections to them other than buying their products.
TOM

Re: Generator head replacement

Reply #5 – February 11, 2023, 10:10:07 am

Quote from: OldManSax – February 11, 2023, 08:50:08 am

I have replaced three generator heads using new ones from Central Georgia Generator. Generator Accessories – Gas Generators | Central Georgia Generators
Tom down there is excellent and they are fair and knowledgeable. I have no connections to them other than buying their products.
TOM

I have looked at them their 11K single bearing is 16" long, won't fit in the space. They are very nice folks.

Re: Generator head replacement

Reply #6 – February 11, 2023, 12:45:02 pm

How many hours did that head last Bruce?

Re: Generator head replacement

Reply #7 – February 11, 2023, 01:41:22 pm

2100 hours. Old age got it. Thats how my
Luck works. Same with the engine processor this summer.

Re: Generator head replacement

Reply #8 – February 11, 2023, 04:05:41 pm

Age and wear is something I understand.

Re: Generator head replacement

Reply #9 – February 11, 2023, 05:10:28 pm

Yup, my voltage has dropped as well.

Re: Generator head replacement

Reply #10 – February 11, 2023, 07:27:17 pm

Quote from: bbeane – February 11, 2023, 10:10:07 am

I have looked at them their 11K single bearing is 16" long, won't fit in the space. They are very nice folks.

That's a shame. The coach I now have has the pancake style head as well. I'm hoping CGG will have them by the time I need one.

TOM

Re: Generator head replacement

Reply #11 – February 11, 2023, 08:03:24 pm

Bruce, looking at your teardown pix, do you think that amount of corrosion is normal for that age genny? Looks like it might have gotten salted in a previous life??? I've talked to folks with 20,000 hours plus on theirs.

Re: Generator head replacement

Reply #12 – February 11, 2023, 09:56:07 pm

Woody, not since I've owned it(2006), never even been on salty roads. I imagine there are a bunch of these generators operating on boats.

Re: Generator head replacement

Reply #13 – February 11, 2023, 10:05:31 pm

Quote from: bbeane – February 10, 2023, 11:16:05 pm

Finally getting around the tearing down the generator. All the testing says the windings are shot.

Which windings Bruce?
Stator?
Rotor?
Exciter?

Do they read open or shorted?

Asking because they don't look that bad to me, I've seen a lot worse. I'm not buying the age thing..... unless the voltage regulator went south and caused an overvoltage/overcurrent issue. That would be a valid reason.

Anyway, hoping you can find a cost effective repair. Wishing you luck on this one.

Re: Generator head replacement

Reply #14 – February 11, 2023, 11:20:43 pm

Justin all diagnoses leads to a defective exciter rotor/rectifier assembly. Voltage not in the specified range while doing the 12V constant excitation test. At any rate it's a moot point as no parts are available for the unit, per powertech. With that said IF you could find some one to rewind/ repair that piece(s), it is likely going to be half the cost of a whole new head. Additionally to test the unit further one needs a meger, and other equipment. Obviously this will cost additional $$ and time. As you can see I'm fast approaching the cost of a whole part. It has been checked by a Powertech shop, and I have been through the troubleshooting with Jeff at PT.

Re: Generator head replacement

Reply #15 – February 12, 2023, 08:23:11 am

Bruce,
Look at the two photos, enlarge them, one is yours the other is a pic of mine when I replaced the main bearing.
There is a resistor or diode connected between the "Q" and "R" connections for the rotor leads, I don't remember which and can't find my schematic on the powertech. I see the two yellow crimp on rings on yours but nothing between them. Maybe its there and I just don,t see it (eyes aint what they use to be)

Re: Generator head replacement

Reply #16 – February 12, 2023, 09:17:29 am

Bruce,did they use a megger to check the windings,if so what was the reading,the windings could possibly need only to be revarnished,we used to use a device that put voltage to the windings to dry them out,if the head will fit in an oven try heating it up for a few hours,won't hurt.Agree about something else may break but you'll have a good engine and head the rest are lower dollar parts.

Re: Generator head replacement

Reply #17 – February 12, 2023, 10:01:13 am

Justin the resistor is there.
A meger has not been used to check the windings. I haven't given up on the head yet. Trying to find a shop that is close enough that has the ability to continue to check and repair is a challenge. As I said being in Yuma kind of puts you at a disadvantage, not a lot of options. What I have found so far, the cost of reworking the old one is nearly the cost of a new one. Just shipping a 150lb part is costly these days. Already been having troubles with this thing for a year and a half, intermittently producing power, and dropping power out under a full load.

Re: Generator head replacement

Reply #18 – February 12, 2023, 07:13:14 pm

If the exciter rotor is the problem, it's not very heavy and should be much cheaper for a generator repair shop to fix, just windings and diodes. Unfortunately PowerTech said the exciter rotor or exciter stator are no longer available. I forget which.....

You commented "testing says windings are shot"
Did they say which windings?

Re: Generator head replacement

Reply #19 – February 12, 2023, 08:08:45 pm

Justin, I'm doing the testing. The 12v constant excitation voltage indicates a problem with the exciter rotor. No Continuity between T1 andT3 indicates an open in the main stator.

Re: Generator head replacement

Reply #20 – February 12, 2023, 08:32:52 pm

Assuming that yours is connected for 120v and not 120/240, what is the ohm value between T1 and T2? also between T3 and T4?
Reading from T1 to T3 assumes a good connection between T2 and T4..........

Re: Generator head replacement

Reply #21 – February 13, 2023, 10:13:19 am

Justin .2 ohms on both.

Re: Generator head replacement

Reply #22 – February 13, 2023, 12:36:18 pm

Quote from: bbeane – February 13, 2023, 10:13:19 am

Justin .2 ohms on both.

That sounds about right, if there was no continuity between T1 and T3 its sounds like a bad connection between T2 & T4 in the control box. They should be connected together and to the Neutral and ground on a stud in the control box.

Sorry to keep bugging you on this Bruce but I would hate for you to spend a whole bunch of coach bucks on a new generator head if there is no obvious problem with yours.

Keep checking and asking questions.

By the way, what voltage regulator do you have? Model number and photo available?

Re: Generator head replacement

Reply #23 – February 13, 2023, 02:13:29 pm

Those reading are with the main stator on the bench. Basler AVR 63 4v regulator, and it is new. The original issue is very low excite/residual voltage in the line side when running 1V + or-. And low output on the line side 71.5 volts during the 12 volt constant excite test. After talking with Jeff at powertech, that indicates a bad excite rotor.

Re: Generator head replacement

Reply #24 – March 06, 2023, 10:16:27 am

Finally got the new generator head. It's not a "plug and play" replacement. Having to have a new adaption plate made at the machine shop, as well as drilling and taping some mounting hole to match the old one. This new generator head is a duel voltage 120/240, the old one was 120 only. What's the down side of running this one at 240v line to line, basically the same as the 50 pole you plug into.

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