# Standby generator problems



## scottknighton (Jun 28, 2011)

Hi guys. I have a briggs and stratton 12,000 W home standby generator. After the gen was installed(propane), the house was abandoned, the gen sat for 5 years. I bought the house with no knowledge of the generator. When the power is off, the gen will start in the auto mode, but shuts off after 20 seconds or so. When the breaker on the gen is off, it will keep running. As soon as the breaker on the gen is turned on, the unit shuts down. I disconnected all wires from the gen and wired the gen straight through, bypassing the transfer switch. Same problem. Tried the oil pressure switch, no luck. I'm convinced the problem is on the generator somewhere. Any ideas


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## telsa (May 22, 2015)

Call for a service tech.

Too many possibilities.

Good luck.


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## scottknighton (Jun 28, 2011)

The only thing is, I'm an electrician myself at a medium size hospital. I take care of 1 750w and two 900w generators. The one at my house is kicking my butt. I thought maybe I could get some ideas before calling in the troops.


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## Jerome208 (May 10, 2013)

You don't say what vintage but this is very curious because B&S generators normally have the voltage sense leads tapped AFTER their main output generator so they will shut down if the breaker is opened or trips on a low voltage code.

What fault code is appearing when it shuts down?

The controller is pretty simple to meter on the ones I am thinking of. It has utility sense leads, gen output sense leads, and a handful of DC wires going to battery, sensor and such. With your skill level you should be able to see whether these are working or hooked up correctly at least.

Some of these are capacitor regulated, others have an active AVR.

The schematic should be available on the B&S site if you punch in your model number.


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## scottknighton (Jun 28, 2011)

Thanks Jerome. The gen has seven 12/2 wires coming from out side. Blue,purple,orange,black and green. All of these are not landed. Two other orange wires are tied into the fault sensor. The sensor will blink(apparently), a number of times. Never seen this work. There is two more wires that terminate on the control board. Disconnecting these and bypassing the switch did nothing.


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## pete87 (Oct 22, 2012)

There is a Website out there for guys who rebuild generators ... a welding site maybe . I have it somewhere , when i find it i will post it .




Pete


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## Jerome208 (May 10, 2013)

It sounds like you are describing a model I am not familiar with.

Can you post a picture or model and serial?



scottknighton said:


> Thanks Jerome. The gen has seven 12/2 wires coming from out side. Blue,purple,orange,black and green. All of these are not landed. Two other orange wires are tied into the fault sensor. The sensor will blink(apparently), a number of times. Never seen this work. There is two more wires that terminate on the control board. Disconnecting these and bypassing the switch did nothing.


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## MDShunk (Jan 7, 2007)

Q: Is this really a Briggs & Stratton generator or some other brand you haven't found on a dataplate; just with a Briggs motor?


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## telsa (May 22, 2015)

There are Sooo many possibilities:

Propane -- icing in the line/ orifice -- every time you fire up ? 

Issues at the tank ?

Is the load upsetting the generator's self protection logic ? 

Some units are wired to drop out under voltage sag. 

Issues with voltage regulation... ?

Without the factory's 'tip sheet' -- you could be chasing your tail for days.


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## scottknighton (Jun 28, 2011)

It's a genuine Briggs and straton. The transfer switch is B&S also. I removed the low volt wires, removed the load wires and the wires from the Gen. I put split bolts and had the Gen wires straight into the load wires. There shouldn't have been anything in the way. It will run all day until I flip the breaker on the unit. Model #01815. The transfer switch is model#071008.


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## Jerome208 (May 10, 2013)

The schematic is here:

http://c.searspartsdirect.com/lis_png/PLDM/P0311061-00007.png

See what kind of voltage you are getting on T1 and T2 with the unit running with the breaker open or closed.

See if you can figure out why L1 is not working.

As you can see it is not a very complicated set of wiring, the answer is in there somewhere.


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## telsa (May 22, 2015)

You wouldn't by any chance be feeding power back into the digital brain that makes the Control Module Assembly think that utility power has been restored ?

This would come to the CMA via the Transformer that normally carries power into the CMA when the generator is not fired up.

It's using that connection to decide when it's time to fire up -- or shut down.

If you permit the gen-set to power up the entire panel -- which would then energize this circuit -- it's just going to turn itself off.


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## nrp3 (Jan 24, 2009)

Look like this?


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## nrp3 (Jan 24, 2009)

The other side:


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## nrp3 (Jan 24, 2009)

So how many blinks of the led when it shuts down when you close the breaker?


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## scottknighton (Jun 28, 2011)

That's the one. I haven't seen any blinks from the led. I have one inside as well. I'm going to pull the entire cover off sat. morning and go from there. Thanks for all you guys help. I'll post and let you know the outcome.


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## nrp3 (Jan 24, 2009)

The troubleshooting guide is available for that and worthwhile if you are going to maintain it yourself. They aren't bad units. What you'll want to do once you get past this problem is to see what the voltage and frequency are. This is a capacitor unit in other words no voltage regulator. Over time these degrade, so for instance it might start, run fine, but no transfer as the voltage is enough to satisfy the board in the generator, but not enough for the board in the transfer switch to transfer. Looking for around 62 hz no load.


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## nrp3 (Jan 24, 2009)

That unit in the picture is one that I pulled from a customers home that wouldn't hold frequency and would fail over or underspeed. One of my buds is going to fix it up and put it up at his camp. The customer has a vertical shaft unit with a new warranty. Almost the same machine with a different controller.


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## GrayHair (Jan 14, 2013)

I'm admittedly out of my limited area of expertise, but several years before I retired, I did a comprehensive report for a emergency generator at the office.

Lets see if I have this right:Propane engine runs fine with no load, but shuts down shortly after load is applied?​If that's the case, the tank could be undersized and unable to vaporize fuel fast enough. It would run lean, overheat and shutdown. Variables in vaporization rate are tank temp, fuel level and withdrawal rate.

Based on 24Kw generator, my 10 year old notes say you need about 480,000 BTU into the engine every hour. With real world numbers from Briggs, a good propane company should be able to tell you if the tank is sized properly.


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## nrp3 (Jan 24, 2009)

I have seen them run for short periods on some pretty small tanks in class with load banks. Its true though they need to take temperature and tank volume into consideration as well as btu consumption of all the appliances and the generator.


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## scottknighton (Jun 28, 2011)

Thanks Grayhair. The only thing is that I'm turning on the breaker with no load at all and it still shuts. Gonna give it the once over twice tomorrow.


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## telsa (May 22, 2015)

Everything you've posted indicates that the gen-set is shutting itself down logically... as in a digital decision.

You might have a failure in a discrete component. 

However, the odds are that some signal current is getting back to the digital brain that it's time to turn off. 

It may be back feeding its own decision logic with its own power... to be confused with Poco power... which it's designed to shut down on.

If you are NOT triggering start up via the ATS then this shut down would not immediately trigger a cyclic pattern of start -- stop -- start -- stop -- start -- stop. It would simply stop. 

Then YOU retry it... and it stops. Repeat as necessary for complete frustration.

Other wise known as the infamous multivibrator. Such dual state oscillations are the bane of electricians all over the planet. ( Typically with the plaint: why is that dang thing flashing ? )

If you've never studied multivibrator circuits -- you should. They are embedded in countless digital devices -- as their dual states are the heart beat of digital logic.


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## Jerome208 (May 10, 2013)

All that needs to be done here is to see if the generator is putting out 240vac 60 Hz (so long as it keeps running) as expected and it is making it to the control board. 

If everything is as expected then the control board is probably faulty.

If 240vac 60 Hz is not being produced then we need to figure out why.

These are expensive so that possibility needs to be proven before throwing parts at it.

One thing to try would be to interrupt the coil grounds somewhere convenient and supply power to the gas valve thus forcing the engine to keep running long enough to get readings off it, if necessary.


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## Aviguy (Feb 14, 2021)

Hi all, I see this is an old post but I have the same generator, and it looks like the same problem and wanted to share what I've found so far: it runs for a few secs and shuts itself off, with the LED blinking three times (low voltage). I opened up the top and side panels, removed the exhaust, and found a bad capacitor on top of the alternator. See attached photo. Part is still on the way, but looking at some other sites it looks like it'll be a good fix.


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## micromind (Aug 11, 2007)

Yep, that's a bad cap alright........lol.


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