Anyone know generators? Generac 15k flashing overspeed light.

[cadunkle]

I have a Generac 15k NG unit, model 0053820 with 188 hours runtime. It starts and runs briefly (maybe 5-10 seconds) then shuts off with a flashing overspeed light. RPM sounds normal. After some research it sounds like flashing overspeed does not indicate overspeed, but rather can indicate an inability to sense RPM through whichever method is used on the particular model or not generating any power. On these smaller air cooled models it seems to commonly be brushes or dirty slip rings. One guy posted on his blog a flashing overspeed was a blown fuse in his transfer switch.

I checked the two fuses in the transfer switch. Both have continuity. The two pop up automotive style fuses on top of the control panel on the generator also both have continuity.

I replaced the brushes and cleaned the slip rings. Slip rings were very dirty. Resistance directly between the slip rings after cleaning was 23.3 ohms. After a few tries starting and getting the same flashing overspeed I measured resistance between pins 9 and 10 on connector C2 (rear of the two connectors into control panel/board area) which I believe go to the brushes. Resistance here measures about 27 ohms.

I'm not sure what to check or try next. I figured brushes were prudent either way since I don't know the history. I didn't mind doing brushes as they were cheap and the maintenance history is unknown on this unit. What do I do next to get this thing working?

 

[jeepxj]

Did you see some posts about ignition coils related to that issue?

 

[cadunkle]

I did. I'm a little skeptical as mine fires right up and runs, granted briefly, with no misfire. Not sure if it's worth $50 for new coils, but I'm debating it.

 

[jeepxj]

I did. I'm a little skeptical as mine fires right up and runs, granted briefly, with no misfire. Not sure if it's worth $50 for new coils, but I'm debating it.

you didnt hear it from me but the amazon rental program is pretty good for tossing parts at a problem until you find the right thing wrong. you got 30 days to find out.

 

[nadogail]

Have you measured the frequency of the output? If you multimeter wont measure frequency use a stopwatch and the Second Hand of an analog electric clock plugged into the generator.

 

[510ebl]

Have you measured the frequency of the output? If you multimeter wont measure frequency use a stopwatch and the Second Hand of an analog electric clock plugged into the generator.

That’s a technique I had long forgotten about, thanks for the reminder.

 

[nadogail]

That’s a technique I had long forgotten about, thanks for the reminder.

You just made an older man feel good, thanks.

 

[vtjon]

I have no idea if this is your solution but I seem to recall having a similar (maybe the same message) a couple of years ago on my 20kw Generac. I hired a tech to fix it but if I recall correctly, a mouse had chewed through a motor control wire. I'm not 100% sure if that was the wire name but it was mouse related.

 

[cadunkle]

I checked voltage and frequency. 184v on one 120v circuit and 61 Hz. It seems like the regulator is stuck full field, and after some reading this is how they typically fail. The older style regulator has been replaced with a newer style that is more finely adjustable and has cooling fins on the case, so I ordered one of those. I suspect this will resolve my problem. Also, reading the manual it specifies for mechanically governed units such as this one to adjust the governor to 62.5 Hz at no load. When the new regulator comes in I'll do that first, then adjust the regulator.

 

[dcg9381]

Have you measured the frequency of the output? If you multimeter wont measure frequency use a stopwatch and the Second Hand of an analog electric clock plugged into the generator.

When you old guys die who are us middle aged guys going to learn from?

 

[nadogail]

When we die you will then be the Old Timers.

 

[AP514]

I suspect this will resolve my problem. Also, reading the manual it specifies for mechanically governed units such as this one to adjust the governor to 62.5 Hz at no load. When the new regulator comes in I'll do that first, then adjust the regulator.

62.5 Hz seems a bit high...I have always thought of 61.5 Hz as the sweet spot.(3680RPM)
But if the manual says so..a good base to start from

 

[Chuckster in NJ]

Have you measured the frequency of the output? If you multimeter wont measure frequency use a stopwatch and the Second Hand of an analog electric clock plugged into the generator.

The problem is finding an analog clock nowadays.

 

[nadogail]

IMHO, if your prime mover (engine) has enough power and your governor has enough sensitivity, frequency stability should not be a problem.

My personal gen set has a 10KW (rated) Harbor Freight alternator spun by a 13 Horse Harbor Freight Greyhound engine made by Lifan.

During trials the speed was adjusted to 60 Hz with no load, the alternator was then loaded with a 1500 Watt heater and my air compressor and the frequency dropped to 59.5 Hz and recovered promptly to 60 Hz. I could hear the engine respond to the load but that is normal.

The rotating mass of the engine flywheel and the rotor in the Alternator assist in maintaing the speed and frequency stability. Flywheel mass is a significant energy source when it is spinning.

 

[cadunkle]

New regulator installed, it stayed running just fine. I adjusted governor to 62-62.5 hz (it varies a couple tenths) and the regulator to get 124v/248v as the service manual calls for. One of these days I'll put a load on it and see if I can fine tune the frequency and voltage at 75%+ load. It's a 992cc twin rated at 30 HP.

 

[Lassen Forge]

When we die you will then be the Old Timers.

Think that's bad? What about those people left behind when YOU die, and THEY become "old timers"... who others look up to for their wisdom...

 

[nadogail]

Think that's bad? What about those people left behind when YOU die, and THEY become "old timers"... who others look up to for their wisdom...

Hopefully before we die we will have taught the kids somethings, including how to think for themselves.

Learning to read and retain some of that will also help.

 

[cadunkle]

This generator developed the same flashing overspeed problem again, intermittently at first and then it would not run when the power went out for a few hours recently. I resolved it by installing a field boost kit, which amounts to a diode and ballast resistor tapped into the 12v DC circuit and installed inline with the brushes.

I'm now having difficulty adjusting the governor. I can get it to maintain a fairly steady RPM at either low load or high load but if I try to adjust the governor as per the manual for 58 Hz at full load it immediately shuts off and errors out with an overspeed light (at 70+ Hz) at no load or low load. I adjusted as per:
1. Loosen governor clamp bolt (See Figure 2.3).
2. Completely remove the idle spring.
3. With governor arm at wide open throttle position, rotate governor shaft fully clockwise. Tighten clamp bolt to 84 inch-pounds.
4. Start unit and apply full load. Use full load speed adjust screw (Figure 2.4) to adjust frequency to 58 Hz.
5. Remove load, stop engine, loosen the idle adjust screw and reconnect the idle spring.
6. Using a hand, push the governor arm to the closed throttle position. Make sure the idle spring does not stretch at all.
7. Restart the unit.
8. Slowly turn the idle adjust screw to adjust the no load idle frequency to 63-63.5 Hz (with door open).
9. The governor is now set.

I don't know exactly how much load I put on it. Lights, refrigerator, and the big load was a 5k watt electric heater. I could have added some smaller electric heat that's on those circuit or my air compressor but I figured that was good enough to get in the ballpark and I could adjust with a higher load if needed. Full load screw to ~58 Hz with that load. When I started it under no load to adjust the idle screw it shut off almost immediately with an overspeed light and was over 70 Hz. I could manually close the throttle to hold 62-64 Hz and it would stay running, but the idle screw is all the way out, only the full load spring is acting on the governor arm.

Everything looked clean but there was some slight resistance in the governor movement. I sprayed the whole governor assembly with WD-40 and worked all parts through their motion, it moves smoothly and easily. Still, I had to back out the full load screw significantly to get 62-64 Hz at no load with the idle screw just shy of acting on the governor arm. I also moved the idle spring one slot toward the governor shaft so it wouldn't act on the arm so quickly and the idle screw ended up more in the middle of it's adjustment range.

I ran the generator under light load and adjusted the full load screw to have 62-64 Hz under light load running lights and refrigerator. It does alright if I add 3k watts of electric heat but if I add 5k watts it gets dragged down to 45 Hz. I'm unsure how to proceed to get the governor to hold speed over a wider range of load. Anyone have experience with this type of governor? Thoughts?

 

[ihateminimumwage]

It's been 4-5 years since I've worked on a HSB Generac so I can't help off the top of my head, but I can shoot you the Diagnostic and Repair manual that goes through all the steps to get everything set right. Just send me a PM with your email and I'll send it your way after work.

 

[cadunkle]

Thanks but already have a PDF of both the installation and owner manual and the diagnostic and repair manual. I don't see anything covering this scenario with widely varying RPM or dragging down under load... Just referencing governor adjustment. It's a GT-990 engine, the older model with mechanical governor obviously.

The valves are a little tappy, I will adjust them this weekend when the engine is cold but I don't think that would affect governor adjustment much. I pulled the spark plugs and they look clean as you'd expect on NG, though one was gapped at .040" and measured ~50k ohms while the other was at .048" and measured ~24k ohms. Resistance seems way high, and that's a lot of gap on the one with lower resistance. Maybe that cylinder was misfiring? Generac calls for .040" gap, I'm thinking I'll compression test and install new plugs at .035". If one cylinder is weak from misfire or low compression it might put things out of range of the governor between full load and no load.

I don't think it would be a gas supply problem since it will hold RPM under load cranking up the full load screw.

 

[Sumboodie]

you didnt hear it from me but the amazon rental program is pretty good for tossing parts at a problem until you find the right thing wrong. you got 30 days to find out.

That's quite dishonest.

 

[Daveyclimber]

Two of my neighbors have these units. Both had issues with the throttle body coming loose and the linkage arm flipped over 180° and caused overspeed issues. Both were LP units. Worth checking I suppose.

 

[jeepxj]

That's quite dishonest.

indeed. anyways.

 

[Doug]

you didnt hear it from me but the amazon rental program is pretty good for tossing parts at a problem until you find the right thing wrong. you got 30 days to find out.

I ran an auto electric business for 40 years. Every now and then I'd have a customer come in with the part I had just sold him and tell me that he had installed it, found out it wasn't the problem, and want his money back. I would tell him that I wasn't in business to provide him with test equipment. People that do this and get away with it do nothing but drive up parts costs.

 

[BillK]

and install new plugs at .035"

Why would you do that if the spec is .040 ????

 

[jeepxj]

I ran an auto electric business for 40 years. Every now and then I'd have a customer come in with the part I had just sold him and tell me that he had installed it, found out it wasn't the problem, and want his money back. I would tell him that I wasn't in business to provide him with test equipment. People that do this and get away with it do nothing but drive up parts costs.

dunno what to tell you. amazon rental program is a thing, right or wrong.

 

[PoorUB]

dunno what to tell you. amazon rental program is a thing, right or wrong.

You can rent books, not generator parts.

 

[jeepxj]

You can rent books, not generator parts.

I dunno what to tell you. people are doing exactly that with amazons return policy.

 

[FredWanaker]

amazon keeps records of purchases vs returns. We've had people on this forum who are banned from Amazon returns. Once that happens they say you are on our list, contact the manufacturer for their warranty.

 

[cadunkle]

Why would you do that if the spec is .040 ????

Seems like a large gap to me. I found another document (https://www.manualslib.com/manual/1040889/Generac-Power-Systems-Gtv-990.html?page=13#manual) for this GT-990 engine in generator applications that calls for .030". A smaller, more typical gap should ensure a good spark if coils are weak or armature gap is off. I wouldn't think NG is that hard to ignite that a .040" gap is required at 3600 RPM.

In any event, I replaced the plugs with the Champion RC12YC gapped at .035". New plugs measure about 5200 ohms, much better than 24k+ ohms. While the plugs were out I compression tested and I have 205 psi on one cylinder and 180 psi on the other. A large difference but within the 25% Generac mentions in the manual linked.

It was dark so I didn't adjust valves or test under load. I will do that in the next day or two and see if it performs better. If it doesn't hold RPM from no load to full load I may try the plugs at .030" and .040" and see if there is any difference in how the governor will hold RPM.

 

[cadunkle]

Two of my neighbors have these units. Both had issues with the throttle body coming loose and the linkage arm flipped over 180° and caused overspeed issues. Both were LP units. Worth checking I suppose.

I don't see how the linkage arm could be flipped. Do you mean the linkage rod? If so I wouldn't think that would change the length but I will remove the intake box and see if anything looks amiss.

 

[ihateminimumwage]

Getting your valves adjusted should bring compression up. They like to get tight over time and hold the valves slightly open. Just re-read through your posts. It sounds like you're getting a pretty wide drop in frequency from not a huge load (would be nice to have an ammeter on those old units).

Have you messed with the governor spring placement at all? That will be your sensitivity adjustment. You already did the governor adjustment/reset and once you know the engine is in good shape I'd adjust there by a slot and see what difference you see.