20 Most Recent Generac Guardian 100 Amp Transfer Switch with Service Disconnect NEMA 3R Questions & Answers

If the generator is out of warranty, you can try spraying a short shot of ether into the intake of the generator as it is running rough. If the engine smoothes out for a few seconds, and returns back to original state, then it is likely running lean. Check the gas regulator (this is LP or natural gas I am assuming since it is standby), the vent may be clogged on the bottom of it.

Generac Guardian... | Answered on Mar 23, 2013

This sounds like the stepper motor is failing with heat. Given the Hz signal is straight from the alternator.... a loss of the signal would intially cause the unit to overspeed. (Wiring from alternator to control board problem maybe... also heat related)
The only thing that made sense to me is a problem in the 10 Ohm freq sensors or the stepper motor.

Noting you have changed the control board and your still having overspeeds Look at the the Hz sense portion. I would bet your shutdonws are being initiated due to over-voltage vs over-speed. That you may have to sort out.

Sounds like a long day... of troubleshooting. 5 - 6 hours wait and then PANIC just to duplicate it!
Hopefully you have the service manual. I have the one for the 15Kw and Up.. but sense circuitry is pretty much the same.

Sense circuit...

* Measure resistance across any combination of orange, yellow, brown, or black should read approximately 20 OHMS.

* Measure from red to any other lead should read 10 OHMS.
* Testing from any lead to stepper motor case should read INFINITY.

Orange or black to Black or green One leg... 20 Ohms
Yellow or Red to Brown or white 2nd leg 20 Ohms

Again Stepper motor or sense wiring / windings... is where I think the problem lies.

Good luck and I am willing to keep taking stabs at this. 40 years as an electrican here.
Thanks for choosing FixYa,

Generac Guardian... | Answered on Sep 03, 2011

I suspect you will SOMEPLACE find protection fuse(s) for the sense lines from the utility. That is the first place to check.

Generac Guardian... | Answered on Mar 04, 2011

Sounds like you missed the low speed jets when you cleaned the carb. They are very small holes and sometimes are behind a plug either rubber or brass.

Generac Guardian... | Answered on Feb 03, 2011

Hi Jake and welcome to FixYa. I am Kelly. Check both CB1 and CB 2 circuit breakers by pushing them to OFF and then back ON. Open the brush block access and then start the unit. You should read voltage at the brushes of 5 - 14 VDC on the terminals of the brushes. If you do not have 5 - 14 VDC at the brushes the probable suspect is the automatic voltage regulator (AVR). If you do have the correct voltages then with the unit OFF.... do a resistance check across the armature coil by reading resistance at the brush block terminals. You should read around 180 Ohms. It can be more or less resistance but for sure less than 500 Ohms. If you do NOT get a resistance reading remove the brush block assy and test the armature directly by reading across BOTH slip rings. You should get the resistance previously stated. If you have resistance then most likely there is a problem with the brushes. (Too short / broken carbon brush / missing spring or a defective terminal.) Without knowing the AVR output voltage and the armature resistance reading at this point it is difficult as to how to advise you to proceed. Let me know the values you obtain for AVR DC voltage at the brushes and actual ARMATURE resistance reading. Make sure you use R x 1000 on the meter. I am having thoughts of maybe a broken wire somewhere inside the control panel also.

Thanks for choosing FixYa,

Generac Guardian... | Answered on Jan 09, 2011

You need to contact TRACE about this endeavor. The inverter will have to work with the generator's control, likely in manual mode. An adapter may be needed for the inverter to allow it to create the signals that the generator expects.

Generac Guardian... | Answered on Jun 12, 2010

How is the battery condition? The click you hear is the starter solenoid pulling in. Check all the connections at the battery, engine ground and starter including the solenoid. You have to 'load test' the battery. Just reading the voltage on the terminals isn't good enough, a near dead battery will read 12 volts with 'no load'

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

Generac Guardian... | Answered on Jul 13, 2009

5 Ohms at the rotor.
Disconnect all the stator wires and measure each one to ground, it should read opened.
Before disconnecting wires, mark which are hot and which are neutral. Measure between the hot neutral wires and some should read at least 0.5 ohms. You should have T1 and T2 reading 0.5 and T3 and T4 reading 0.5. T1 and T3 should read opened, T1 to T4 should read opened. Also, T2 to T3 should be opened and T2 to T4 opened.

Generac Guardian... | Answered on May 07, 2009

Natural gas and Propane engines do create moisture in the engine because these are cold gases. Therefore, when the engine is done running, the engine is hot and whatever gas is left will condensate and the moisture will drop to the bottom of the engine or oil pan. If this is using these gases then it is normal what you are seeing.

Generac Guardian... | Answered on May 07, 2009

That sounds just about right, if the relay contacts get welded together it sometimes takes out the driver on the printed circuit board. As you found out, 12vdc from 23 to 194 makes the transfer switch move to the Generator position, relay not energized makes the ATS move to the Normal position.

You can make a nice test function by installing a 10 amp contact switch in series with either the N1 or N2 terminals. When the switch is open the generator thinks the Normal power has failed.


Generac Guardian... | Answered on Jan 26, 2009

its the problem of the switch and it has to be replace in such cases to make it proper.it is necessary to replace the switch.

Generac Guardian... | Answered on Dec 25, 2008

Regarding the advice about "Flashing" a generator.
Do you people even know what that means?

What you are doing is messing with the capacitor that is part of the voltage conversion. Likely you are burning any shorts out of the capacitor. Has noting to do with the fields or coils or rectifier.

So if you are having issues then test the capacitor and replace it.
Try your flashing and see if you don't fry the rectifier.

It amazes me that people will blindly follow something they don't understand "hoping" that something good will happen.

But if a new generator is what you want then give your old one away instead of trashing it.

Generac... | Answered on May 13, 2020

During engine cranking and operation the controller receives AC
voltage and frequency signals from the ignition magneto via Wire
18. Should the speed exceed approximately 72 Hz (4320 RPM),
the controller's logic will de-energize the "run relay" (internal to
the controller). The relay contacts will open terminating engine
ignition and closing the fuel shutoff solenoid; the engine will
then shut down. This feature protects the engine and alternator
against damaging over speeds. During cranking the RPM signal
generated by the magnetos is used to terminate engine cranking.

Generac... | Answered on May 09, 2020

If you have a Generac Generator which fails to start during a power outage and gives an Error Code 1518 - RPM Sense Loss you can try and manually get the generator restarted very simply. ... The generator should wait 5 seconds and then try and auto-start up to 3 times.

Generac... | Answered on Mar 25, 2020

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