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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14436
Experience:  Certified on Onan and Generac generators
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Hello, I have a Generac NP-52G gas generator in a motorhome.

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I have a Generac NP-52G gas generator in a motorhome. Ran fine till last trip, stopped producing AC power. I've read through many of your answers, and starting checking things but thought best to start with you from scratch. So with breakers off, clean fuel, oil level correct it starts immediately, runs about 15-20 seconds and shuts down. During this time A/C voltage output is around 35-40 volts, red LED on regulator flickers but is not a steady bright glow. Please work your magic :)
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My name is XXXXX XXXXX I am going to assist you with this.

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Now with that being said, let’s find and fix your problem.



What is the serial number of the genset?

Where are you measuring the voltage at?
Customer: replied 4 years ago.
Hi Hank,
Ser# XXXXX I am measuring the voltage on the inbound (line?) side of the

the breaker-
Good deal - that is exactly the best place to test at, as it bypasses everything else in the electrical system.

But we do have a small problem. You missed one digit of the serial number - there should be 7 digits.
I will also need the Item Number from the data label. There are several different model numbers that wear the NP52G label.
Customer: replied 4 years ago.
Looked carefully and there are 2 data tags on the lower left hand side as you are facing it. Upper tag has the following info- Mod 303775 Type 0119-014011 Code 90101311 Lower tag has the following Model 9202 0 and Serial 116695

If this helps, I put a better meter on it and the voltage is steady at 48-49 volts. Fuel pump is only getting power during start cycle, (hence the shut down??) I jumped power to fuel pump and it runs indefinitely but still 48-49 volts. Hope you had a good 4th!

Yes, sir, I had a pretty good 4th, even though the heat was sweltering.
Hope yours was even better than mine....

The first data tag you are referring to is the engine ID number. This engine is a Briggs and Stratton design.

The second tag is the one I need.
Unfortunately, I am well familiar with this particular genset.
The electric side of it is not all that bad to work on, but hope and pray that you never have to do any engine work - especially an exhaust manifold. This thing is the biggest pain I have ever worked on.

What I would like you to do is a procedure called a Fixed Excitation/Rotor Amp draw test.
Please do all of the steps in test #4, and let me know all of the results.
When giving the results, please give me the wire numbers, and not the step numbers.
IE - Wire 2 to wire 6 gave 62V, not step 5 gave 62V.

Also, do not pay attention to the results chart in the upload. This test was actually written for a different genset, so the charts are different, but this set of instructions is much easier to follow.
Click here to download the instructions.
Customer: replied 4 years ago.
Hi Hank,
My layout was a little different than the schematic- only 1 wire #4 and #162

was just #2 on mine. My wire#2 left the regulator and headed out toward the inaccessible part of the generator. I went through the schematic and could not find anything labeled excitation circuit breaker, so no way to unplug #2 from it to perform test #1.

With 12 volts jumped to #4, wires 11 &22 now give 89-90 volts AC.

Wire #4 (motor not running) showed -684 on the mA setting, and 0644 (motor running). In both cases with motor running I'm still jumping 12v to the fuel pump.

Meter I'm using is a Fluke 87

The excitation breaker is labeled CB3 on your schematic.
It looks just like the picture in the download I gave you.

The number 2 wire on your regulator should actually be numbered 2A.
Wire 2 comes out of the stator, to the excitation breaker, and from the excitation breaker it is wire 2A to the regulator.

But if you were getting 90 volts out of the set when jumping 12V to wire 4, it means the rotor and stator are ok, and the voltage regulator is bad.
Customer: replied 4 years ago.
Thanks for the prompt reply- better the regulator than the stator or rotor! Will replacing the regulator also solve the no power to the fuel pump except on startup?
Yes, it should, if there are no other problems.
When the genset is running, it takes some of the power from the alternator, and changes it to DC power for the fuel pump and choke heater.
What is happening is that while cranking, the engine control board bypasses all of this, and manually puts 12V to the pump.
When you let off the start switch, the pump stops - but there is still enough fuel in the carb for the engine to run for a few seconds.
Hank F. and other Small Engine Specialists are ready to help you
Customer: replied 4 years ago.
Not that you didn't already know this but got the new regulator installed last night and it works perfectly- Thank you again!!!!
Not a problem at all, my friend. That is why we are here.

And thank you for the update - we are always glad to know what happens,