frank_des_jardins
8kW Air-Cooled
Model #: 0058700
Serial #: 6077396

It's been two weeks in a row that my generator gives me a RPM sensor loss error during its weekly exercise. It actually does not run during its exercise and I think it defaults to this code. However, I reset the error code and can run the generator in manual mode every time. The starter turns and the engine starts right away on the first try and then I ran the generator 10 minutes without any error codes. Where do I start my troubleshooting?

With no major load on the generator, I have measured the voltage at the 240v leads and get variations in the voltage +/- 15 volts. Wondering if this can be related and if it is normal?

Thanks,
Frank
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Skip Douglas SkipD
What meter (make and model) are you using to make the voltage measurements? The reason that I ask is that a lot of cheap digital multimeters cannot read the voltage from the generators properly.
Skip Douglas
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MikeCB
Go to History and look at your "run" and "error" logs. Compare how much time (in seconds) passed between the exercise start event and when the RPM sense fault occurred. I'm willing to bet it's only a matter of 2-3 seconds tops. If that's the case, my money is on a bad starter contactor.
Over the past year or so I've suddenly had to replace a TON of starter contacts from 8kw units the same age as yours. I think it's just their time.
In my experience the contactors begin to fail intermittently but get to the point where they won't work at all. The unit starting in manual but not automatically is probably just coincidence. Force a few exercises by setting the clock a minute or two before it's set to run just to be sure.

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Peddler
My bet is on a bad coil. I have had a ton of these faults and it has been a coil in the end. They will start in manual but when it comes to exercise they won't start. It is possible that it is the starter contactor but why would it always start on manual? Good Luck, Peddler
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MikeCB
Manual still requires a speed reference from wire 18 though. Failed coil would cause fault regardless of mode.

Edit:: if the coil is failing to fire you would get an overcrank instead of RPM.

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frank_des_jardins
Can someone point me towards the right contacter and coil for my model? I'll change these and see if the error goes away. Is the contacter just a relay to switch a high dc voltage with a low dc voltage? ow the m
Also if someone knows the maintenance kit I should purchase (spark plug, oil filter and air filter) please let me know.
Thanks for the advice. Oh and I will check the meter's model tomorrow.
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nrp3
Contactor:

[url]https://www.zillerelectric.com/products/generac-086729-starter-contactor[/url]

coil:

[url]https://www.zillerelectric.com/products/0g9241-0g9241t-ignition-coil[/url]

Maintenance kit:

[url]https://www.zillerelectric.com/collections/generac-maintenance-kits/products/5662-or-0g95280srv-generac-maintenance-kit-for-8kw-models-5882-5870-5501-5518-home-standby-generator-410cc-kit[/url]
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MEC
As he others mentioned
Contactor
Starter

If it were me I'd do the contactor first and then the battery if it needs it.
Since this is a Nexus model, you should replace the battery every 4yrs.


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frank_des_jardins
Generator missed its weekly exercise again but I have not changed the parts yet, I've ordered the contactor and the coil (the parts where not too expensive so I just ordered both). I exercised it manually by resetting the RPM error code and turned off the breaker to the critical load sub-panel. Generator started during its second crank try.

I'm not the original owner of the generator but I do know that the battery (and maybe the starter) was changed about 2 years ago.

@SkipD my meter is a Pro's Kit MT-1230N. It seems like the voltage stabilizes once a load is turned on, like a microwave.
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DenisC
The contactor solved my 8kw RPM sense error code. The contactor problem was intermittent. After several times starting it in manual I heard a heavy "click" but the starter didn't power up.
I did the same as you and replaced both the contactor and the coil. I gapped the coil about .010 inches from the magnet.
Everything working good now.
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MEC
Congrats!


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bobt2382
DenisC;n47740 wrote:
The contactor solved my 8kw RPM sense error code. The contactor problem was intermittent. After several times starting it in manual I heard a heavy "click" but the starter didn't power up.
I did the same as you and replaced both the contactor and the coil. I gapped the coil about .010 inches from the magnet.
Everything working good now.


Just got my parents 7KW generator back up and running properly after an RPM sense error code and difficulty starting. Replaced the battery, unknown age but at least 5 years old. Ordered the two parts MEC linked to from Ziller. Only installed the contactor and properly adjusted the valve lash to .003. They were tight! Generator started right up!

Thanks to all for posting questions and to the technicians for providing guidance.

BTW, I didn't have a 10mm allen wrench so I used a T-55 internal torx socket. Worked fine as an allen wrench replacement.
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