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Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Industrial Equipment
Satisfied Customers: 14487
Experience:  Certified on Onan and Generac generators
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I already told you and you never replied, I have an older

Customer Question

I already told you and you never replied
JA: Sorry about that. I must have missed it. Could you tell me again?
Customer: I have an older 20kw generac that's only putting out 2 volts. I've disconnected the voltage regulator and put 12v dc to the brushes and the results were the same
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: Ring to ring resistance on the rotor is 10 ohms
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: The generator was supposedly working fine before I got it but it has sat for some time
JA: What's the make and model of the generator? And can you guesstimate how old it is?
Customer: Generac 93A 01912 S, the year is 1993
Submitted: 3 months ago.
Category: Industrial Equipment
Expert:  Hank F. replied 3 months ago.

What is the serial number of the genset?

Customer: replied 3 months ago.
93A 01912 S, it is an industrial 20k generac, natural gas model
Expert:  Hank F. replied 3 months ago.

Sorry, I only work on a few industrial units, and this is not one of them.

I will opt out.

Customer: replied 3 months ago.
That's anyway man
Customer: replied 3 months ago.
I have the wiring diagrams for the engine, control panel, and alternator itself if that would change your mind, I can send them your way
Customer: replied 3 months ago.
Maybe these will help
Expert:  Hank F. replied 2 months ago.

I have been contacted by a moderator, who told me that no one has been able to help you.

As I stated, this is not a unit I am familiar with. I am not certified on H-panel units, and have only worked on a few. I have not ever worked on one like yours.

However, due to the fact that no one else seems interested in helping you, possibly due to the low offer you made, or maybe no one here knows that unit, and the fact that moderator has gone over the top to be nice to me over the years, I am going to do her and you a favor and try to help you.

Please do not be too upset if we can't get to the bottom of this. I will try, but I can't guarantee anything.

Before I can help, though, I need some additional information.

1. What is the serial number of the genset?

2. What voltage and phase is it set up for?

3. Do you know if this unit has a 4 lead stator, or a 12 lead stator?

Customer: replied 2 months ago.
Thank you for replying! I didn't set the amount, I just payed it when the site told me how much...93A 01912 SIt is configured for 120/240And I'm sorry I do not know if it's 4 or 12, would this be the total number of wires coming out of the alternator?
Customer: replied 2 months ago.
It's single phase, there are 2 hot wires and a neutral coming out of the alternator although the controls panel does have a "phase selector switch" it doesn't move from the single phase position
Expert:  Hank F. replied 2 months ago.

93A 01912 S should be the model number, isn't it?

Is there any chance you can get a good photo of the data plate, and post it here?

A 4 lead stator will have a total of 7 wires coming out of it.

A 12 lead stator will have a total of 15 wires coming out of it.

When referring to the lead count, control wires are not counted - only power wires are.

Customer: replied 2 months ago.
Looks like a 4 lead. I count a total of 7 not including the 2 wires that go to the brushes.
Customer: replied 2 months ago.
Sorry you're right, here's the serial
Expert:  Hank F. replied 2 months ago.

OK.

At the main circuit breakers, disconnect wires 11 and 44 (only the stator leads).

At the ground bus, disconnect wires 22 and 33.

At the voltage regulator in the control box, disconnect wire 6.

At the DPE breaker in the control box, disconnect wire 2.

Separate and isolate all leads, so they can not touch anything.

Set your meter to ohms, on the lowest scale possible, and test across the following points:

Wire 11 to 22

Wire 11 to 33

Wire 11 to 2

Wire 11 to ground

Wire 22 to wire 2

Wire 22 to ground

wire 33 to 44

Wire 33 to ground

Wire 2 to 6

Wire 2 to ground

What readings do you get on all these?

I would also like to to again ohm across the slip rings, just to verify your original reading.

Customer: replied 2 months ago.
Sorry for the delay I've been away from the machine.11 to 22 is .2 ohms11 to 33 is open loop11 to 2 is open loop11 to ground is open loop22 to 2 is open loop22 to ground is open loop33 to 44 is .1 ohms33 to ground is open loop2 to 6 is .7 ohms2 to ground is open loopRings lowest measurement was 8.8
Expert:  Hank F. replied 2 months ago.

The 8 - 10 ohms across the slip rings seems low to me. The stator readings all look good.

Let me try again to get the specs on that rotor. I am having trouble getting them, because as I stated, I am not certified on that unit, and Generac doesn't want to give out that info to me.

Customer: replied 2 months ago.
I can give you the email of the guy I got the diagrams from, it took me a lot of phone calls to find someone who knew anything about it and I think I ended up at southeastern power suppliers or something like that but I still have his email
Customer: replied 2 months ago.
Expert:  Hank F. replied 2 months ago.

Check the gen end of your unit. Is there another tag on it anywhere that lists the alternator ID and any specs?

Also, coming out of the stator, there is a wire #5. Trace it down. Is it connected to a small device on the alternator, or is it terminated in a wire nut?

Customer: replied 2 months ago.
There is a number 5 and it does end in a cap, these are the only other tags on the generator
Expert:  Hank F. replied 2 months ago.

Yes - that is the tag I needed.

Let me do some more research on this one.

Customer: replied 2 months ago.
Alright thanks!
Customer: replied 2 months ago.
No luck?
Expert:  Hank F. replied 1 month ago.

Sorry, I never got notified that you had replied.

And I lost the link to this thread.

Have you gotten anywhere with this, or are you still working on it?

Customer: replied 1 month ago.
No I haven't I'm an automotive mechanic but I'll admit my knowledge of AC electricity is primitive at best.
Customer: replied 1 month ago.
What about the rotor reading? Where should I go.from here?
Expert:  Hank F. replied 1 month ago.

I have contacted Generac directly, and they said they couldn't help me, and passed me off to our local industrial distributor. I have worked with 2 people from there, but your unit is too old, and they can't get any info on it.

You stated earlier that you got 10 ohms across the slip rings.

I would like you to install the brush block, and test from brush to brush. What resistance do you get there?

When you jumped 12V directly to the brushes, what did you use as a power source, and where did you run the ground to?

Customer: replied 1 month ago.
I used a jump box and just connected positive lead to the red brush wire and the negative lead to the black brush wire
Customer: replied 1 month ago.
I will get you a resistance reading in a few
Expert:  Hank F. replied 1 month ago.

Ok.

Customer: replied 1 month ago.
From brush lead to brush lead I'm reading 1.3k ohms, I didn't notice this before
Customer: replied 1 month ago.
From negative lead to brush is .3 ohms but from negative lead to ring is .6k ohms, the positive is nearly the same, the loss is in the brush to ring connection
Customer: replied 1 month ago.
I just spun the generator over and the resistance dropped significantly, lead to lead is now 27 ohms
Customer: replied 1 month ago.
Spun again and dropped to 17 ohms so I guess that excessive resistance was from sitting?
Expert:  Hank F. replied 1 month ago.

You may have contaminated brushes, but most likely have dirty slip rings.

Clean the rings and try it again.

Resistance through the brushes should be the same as resistance across the slip rings.

Maybe dirty rings is all the problem there has been.

Let me know what happens.

Expert:  Hank F. replied 1 month ago.

Have you tried this yet?

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