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Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15267
Experience:  Certified on Onan and Generac generators
19372534
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Won't run. error msg "not sensing RPM" 6-7 years. this error

Customer Question

won't run. error msg "not sensing RPM"
JA: How old is the appliance? Have you gotten error messages before?
Customer: 6-7 years. this error present for two months
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: just need to know how to get rid of the error msg
Submitted: 1 month ago.
Category: Small Engine
Expert:  Hank F. replied 1 month ago.

Hello, my name is ***** ***** I am going to assist you with this.

What type of equipment is this/

Brand?

Model number?

Serial number?

Customer: replied 1 month ago.
generac.
5870(###) ###-####
Customer: replied 1 month ago.
also, this is a stand by generator
Expert:  Hank F. replied 1 month ago.

That's ok. I am certified an all Generac air-cooled units up to 60kW. It doesn't matter if is a portable or a stand by.

First. lets see if we can do a simple reset.

Turn the switch to OFF.

Pull the fuse out of the control panel, and wait 10 seconds.

Put the fuse back in.

Set the switch to MANUAL.

Will the unit run now?

Also, by doing this, you will need to reset the exercise timer, as removing the fuse will erase the memory.

Customer: replied 1 month ago.
the engine started, ran for about 5 sec, turned self off. error msg re: not sensing RPMs THANKS
Customer: replied 1 month ago.
It still does not work. What do you suggest?
Expert:  Hank F. replied 1 month ago.

Ok.

You need to connect an AC voltmeter to the back of the circuit breakers, and start the genset.

How much voltage is it producing for the few seconds it will run?

Customer: replied 1 month ago.
I do have a voltmeter. Lets skiip this on and go forward.
Customer: replied 1 month ago.
the generator will not restart.
Expert:  Hank F. replied 1 month ago.

I need to know the voltage output - that will tell us where we need to go next.

Customer: replied 1 month ago.
Can we do the volt test tomorrow?
Expert:  Hank F. replied 1 month ago.

You can do it when ever you are able. There is no time limit on this.

But be advised that I work 2 day jobs, and normally help on Just Answer in the evenings. Tomorrow I have my long job, and work 6:30 AM to 7 PM, and won't be able to respond until tomorrow evening.

Customer: replied 1 month ago.
Hank, I will try to get the information for you tomorrow, the 12th. Will have to borrow a voltage meter. Thanks, Mary
Expert:  Hank F. replied 1 month ago.

Not a problem at all.

Customer: replied 1 month ago.
The voltage was -0- when tested on the house side of the circuit breaker while cranking.
Expert:  Hank F. replied 1 month ago.

You need to test on the input (generator side) of the breaker.

This rules out a bad breaker, and everything past it.

Customer: replied 1 month ago.
How do I test on the generator side. We found only one place, and that was near the power On/Off.
Customer: replied 1 month ago.
where is the generator side. Thanks
Expert:  Hank F. replied 1 month ago.

There are 2 wires on each breaker. One is the input from the stator, the other is the output to the transfer switch.

You need to be testing the stator input side.

Customer: replied 1 month ago.
The generator started on manual, ran for about 30 sec and stopped with low voltage alarm. Tested the stator and showed No voltage.
What color is the wire off the stator? Two black ?
Expert:  Hank F. replied 1 month ago.

There are 8 wires that come off the stator.

The 2 large black ones that go to the circuit breakers are numbered 11 and 44. The 2 large white ones that go to the neutral bus are numbered 22 and 33.

The other 4 are small control wires that go to the engine to control connector.

Customer: replied 1 month ago.
It appears that we tested the stator and there was no voltage.
Expert:  Hank F. replied 1 month ago.

Ok.

I have uploaded as series of tests for you to do.

Please do all of the steps in Test 4 - Fixed Excitation/Rotor Amp Draw, and let me know all the results.

Click here to download the tests.

Expert:  Hank F. replied 1 month ago.

Have you done the tests yet?

Customer: replied 1 month ago.
I am sure that this problem, "not detecting RPM" has happened before and there is an solution that does not require forever testing. Thanks.
Expert:  Hank F. replied 1 month ago.

There are several things that can set the code. Testing is the only way to find out what is causing it.

There is no such thing as a magic cure.