# Harbor Freight – Predator 9500 Invertor Generator



## EJ3 (4 mo ago)

A little over a year ago I bought a Predator 9500 inverter generator. I broke it for 30 hours and changed the oil. Since then I have run it once every 2-3 months for at least 30 min. The fuel has Sta-Bil added.

On Monday 09/12/22 the power was out early in the morning. The generator fired up but cut off after about 20 seconds. When it would shut down the red oil alarm light would come on. It did this 5-6 times before I gave up. The generator only had 33.8 hours on it. The oil level is correct and the unit is on level ground. I tried reaching out to HFT tech support on the phone with no answer. And I sent an email to product support with no answer. 

I had read and seen on YouTube that if the low oil sensor is clogged or bad it will cause this issue. So on Tuesday afternoon I tried disconnecting the yellow wire at the sensor. It still started and ran for about 20 seconds before shutting down. The red oil alarm light would come on as before. I also noticed that the CO light flashed yellow. The generator was outside with more than ample clearances. After a few attempts I finally got it running and it ran for about 1.25 hours. 

Well on Wednesday I tried starting it and now it will not even start. The low oil light comes on, but no lights at the CO indicator light.

Yesterday I finally received a call from HFT tech support. Based on what I described, he feels it is probably a bad CO sensor. They are sending me a new sensor. Hopefully this will solve the issue.

Regardless, I am considering bypassing both the CO and oil level sensors. Looking at the attached photos, does anyone see what wires should be disconnected/modified? Obviously doing so would be my responsibility/liability. I have not been able to find a detailed wiring diagram.

Any help would be greatly appreciated.


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## OrlyP (Oct 19, 2021)

Just know that bypassing safety systems is not the best way to go about it. That said, I can understand your motivation to do so. Just be aware of the consequences when carrying out such drastic methods.

If the generator is solely going to be operated in an open area (as it should be) and away from living spaces, you could probably be fine with the CO alert disabled. From what I've read, simply disconnecting the wire connector behind the CO module essentially bypasses it.

As to the oil level alert system, there are two or maybe three parts that can go wrong. Most common failure point is the oil level sensor inside the crankcase. 2nd failure point would be the oil sensor module. This is a part that ressembles a small automotive relay, except that it is often encased in metal. It's often found bolted on the engine near where the yellow wire from the sensor goes to. If in doubt, just follow the yellow wire. If the oil alert circuitry is built into the inverter module, that gets us to the possible third cause of failure. The inverter module may be faulty. Without looking at the schematic, I'm willing to bet that your generator has a dedicated oil sensor module (ie. not integrated with the inverter module).


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## FlyFisher (Jun 30, 2018)

Get you a multimeter unless you already have one. If you unplug the sensors and it doesn't work you need to figure out what the signal is that the controller is looking for from those - a voltage/resistance for example. If that is the case you might be able to trick the controller by using a resistance value to mimic the sensor. You'll need a multimeter to figure that one out.


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## iowagold (Jan 22, 2020)

just a BIG disclaimer note on the c/o
bypass oil sender and c/o sensor at your own risk.
and make sure to run a c/o detector in several places in the house.
as well as on the lowest level.
in other words "Never do this at home kids" GRIN!

ok 
on to the ckt
yea some work just like the oil sensor as ground out the spark when detected.
so removal of the sensor output wire works for a test by pass.

some of the new inverter gens now have the oil and c/o sensors integrated with the inverter or spark unit for a new twist...
part of the new liability thing for 2024-2025...

so yes you need a meter and a couple of test lights and walk down through the wiring.
and if you have a factory wiring diagram that is a BIG help!


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## OrlyP (Oct 19, 2021)

Although I'm _personally_ ok disabling the on-board CO sensor, which to me is just a trivial attempt from manufacturers to be able to comply, don't do it unless it interferes with the operation of the generator.

However, I can never stress enough why having several CO detectors around the house is deadly important. Even if you think you've done everything to keep those fumes out, don't bet your life on it. Have a 2nd or even a 3rd layer of protection, always.

Also plan ahead with your family on what to do when those detectors go off. It might differ depending on where you are. Apparently in the US, you're supposed to call the fire dept. so they can check it out with their own detector to tell you if there's any real danger or if it's just a false alarm.

This is a good watch. This is how sneaky CO gas can be... literally.


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## Colt Carson (6 mo ago)

On kind of a related subject…
my neighbor across the street had a propane gas grill in his garage, and apparently he didn’t shut off the tank valve when he wasn’t using it. A friend came over and while they were talking, the friend leaned against the grill with his butt and unknowingly barely turned one of the grill's knobs. Sometime later (day or two?) my neighbor's daughter wasn’t feeling well. They investigated and found the smell of propane, and the leaking grill burner. The propane gas had somehow permeated the garage wall and seeped into the daughter's bedroom. Maybe they were running a clothes dryer in the house, causing a slight vacuum. The garage contained an operational natural gas water heater. The only thing I can figure that prevented an explosion, is that the water heater was elevated off the floor. If propane can find a way into that house, so could carbon monoxide. You don’t know what you don’t know. Keep engines away from the house and be safe!


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## GenKnot (Dec 20, 2021)

He missed a few other things that are potential issues. The homes have soffit vents which could allow exhaust gas entry into the attic space which has many penetrations into the wall spaces and other areas inside the house. In many homes with natural gas or propane water heaters, furnaces, etc., the intake air is from the attic. He also didn't mention the neighbor's house. How would the homeowner know that the neighbor is not being poisoned by his generator thru his soffit vents, air intakes or open windows? This is an example of a very bad generator installation.


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## EJ3 (4 mo ago)

OrlyP said:


> Just know that bypassing safety systems is not the best way to go about it. That said, I can understand your motivation to do so. Just be aware of the consequences when carrying out such drastic methods.
> 
> If the generator is solely going to be operated in an open area (as it should be) and away from living spaces, you could probably be fine with the CO alert disabled. From what I've read, simply disconnecting the wire connector behind the CO module essentially bypasses it.
> 
> As to the oil level alert system, there are two or maybe three parts that can go wrong. Most common failure point is the oil level sensor inside the crankcase. 2nd failure point would be the oil sensor module. This is a part that ressembles a small automotive relay, except that it is often encased in metal. It's often found bolted on the engine near where the yellow wire from the sensor goes to. If in doubt, just follow the yellow wire. If the oil alert circuitry is built into the inverter module, that gets us to the possible third cause of failure. The inverter module may be faulty. Without looking at the schematic, I'm willing to bet that your generator has a dedicated oil sensor module (ie. not integrated with the inverter module).


Thanks for all of the replies. I am hoping to avoid disabling any safety components. I finally spoke with a tech and he feels that I have a bad CO sensor. He said that it can also cause the low oil alarm light to come on. They are sending me a new sensor (not rec'd yet).

Attached is the wiring schematic I received. It appears that the CO alarm runs through the oil alarm module. So I will try the replacement CO sensor first.


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## EJ3 (4 mo ago)

Received and installed the new CO sensor this afternoon. It fired up and ran like new. HFT even included a couple of tools. Nice touch!

The Predator 9500 will run my 3 ton AC unit, well pump, multiple refrigerators, freezers, TV and lights. But I did have to install a 5-2-1 Compressor Saver.


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## Miles (2 mo ago)

Thanks for starting this thread EJ3! It saved me a lot of troubleshooting. I had the same symptoms and and run time on my Predator 9500. Called HFT tech support and they indicated the CO sensor failure is proving to be a chronic issue with this model. They shipped me the new part (bonus tools included), asking only for name and shipping address (proof of purchase and S/N not necessary). Replacement was easy (from the Oil Fill Access side). Like yours, it fired up and ran like new.


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