GP15000 'Portable' Surges

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
Chris
Site Admin
Site Admin
Posts: 3536
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

In looking at the video, I don't think that's a stepper issue. It moves smooth and is reacting to what it's being told to do. Normally a stepper would show jitters or no movement at all if it were faulty.

So that leads us back to a fuel issue, or some type of control issue (in my opinion). Have you tried running the unit with no air filter installed, or running it by partially blocking one of the intake ports on the carb with a finger to modify the air fuel mix a bit. I don't think I've ever had a customer make the complaint that the control board was making a unit surge, but I could be wrong!

If you look at page 34 in the manual under the 'Engine hunts' section, have you checked and performed the tests listed there?
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
William1
Contributor
Contributor
Posts: 28
Joined: Sat Feb 20, 2021 10:47 am

Chris wrote:
Tue Feb 23, 2021 9:15 am
In looking at the video, I don't think that's a stepper issue. It moves smooth and is reacting to what it's being told to do. Normally a stepper would show jitters or no movement at all if it were faulty.

So that leads us back to a fuel issue, or some type of control issue (in my opinion). Have you tried running the unit with no air filter installed, or running it by partially blocking one of the intake ports on the carb with a finger to modify the air fuel mix a bit. I don't think I've ever had a customer make the complaint that the control board was making a unit surge, but I could be wrong!

If you look at page 34 in the manual under the 'Engine hunts' section, have you checked and performed the tests listed there?
Yup, I have run it with no air filter. I have run it varying the choke in tiny increments.
I will try to partially block a carb port though I'd think the choke would of done the same.
Spark plugs have been replaced. Old ones looked good, just they were old.
Oil/filter is changed every year.
Idle is fine, It is a 'no load' condition as well.
I have NOT checked or adjusted the valves.
Unit is stored inside and when run, it out under an over hang, so it never gets wet.

The only 'give away' (and I need to recheck to confirm) is that it only hunts when a load is applied. IIRC, when max load is applied, the throttle gets 'pinned' and no surge. The size of the load does not appear to be what does it. I'll find something that draws under 100 watts and try that once the temps outside rise above freezing.

My 'guess' would be a bad control board or something amiss in the carb. I have extensive powersports experience and I do not think it is the carb. IF I hold (restrict from moving) the stepper, the engine sounds fine. My guess is the throttle (is moving too fast), over shoots, then (moves too fast and) undershoots. But I am no expert on these, so....
Chris
Site Admin
Site Admin
Posts: 3536
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

There is a section in the manual which talks about checking the idle control transformer on page 62. That may be a good test too, just to make sure nothing is funny with the CT. If I read your reply correctly, it sounds like in 'idle mode' (when the unit idles down) it runs smoothly as well?

I honestly don't know if the CT is used for speed regulation on these units other than to sense if there is load or not for the idle control. If it is, it's not mentioned in the operation analysis, just that output voltage on the sensing wires is used. If that's true, then it may in fact be the control board that's not acting correctly.

It would be interesting to see what happens if you disconnect the stepper motor from the controller and move the stepper manually to around 60Hz and let it run, how it actually runs and what the output voltage and Hz are measured at.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
William1
Contributor
Contributor
Posts: 28
Joined: Sat Feb 20, 2021 10:47 am

Chris wrote:
Tue Feb 23, 2021 10:31 am
There is a section in the manual which talks about checking the idle control transformer on page 62. That may be a good test too, just to make sure nothing is funny with the CT. If I read your reply correctly, it sounds like in 'idle mode' (when the unit idles down) it runs smoothly as well?

I honestly don't know if the CT is used for speed regulation on these units other than to sense if there is load or not for the idle control. If it is, it's not mentioned in the operation analysis, just that output voltage on the sensing wires is used. If that's true, then it may in fact be the control board that's not acting correctly.

It would be interesting to see what happens if you disconnect the stepper motor from the controller and move the stepper manually to around 60Hz and let it run, how it actually runs and what the output voltage and Hz are measured at.
The idle control switch does work as designed. No load, the generator slows down. Apply a load and it speed back up. I have not confirmed if engaged, the generator runs smooth under load. I will try that later.

'Something' has to act as a governor to maintain frequency and output voltage. As load increases, RPM would drop (as would output voltage and frequency along with an increase in amperage draw), requiring more air and fuel to maintain engine speed. This should occur right up to 100% engine power use at which point the engine speed would drop (and probably stall) from excessive load. Do you think I am being logical?

My old WINCO, had just the crude mechanical governor that held RPM. Not real accurate. That genset had a throttle lever, either at idle or you opened it all the way manually. The mechanical governor kept rpms at 3600, more or less.
Chris
Site Admin
Site Admin
Posts: 3536
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

The controller and stepper work together to maintain speed. They are pretty simple creatures. Basically output Hz is monitored and when it droops, the stepper speeds up the engine until it hits 60Hz and then tries to maintain it there. Hz is based on engine RPM, so 60Hz = 3600 RPM for a 2 pole generator rotor like this one. I don't think it uses the CT for any of that, but figured it was worth a shot asking about the idle control.

They used a similar stepper controller on older liquid cooled models. That stepper controller looks very similar to your controller, but basically just gets 12V power, a voltage output signal from the gen, and has an output for the stepper, that's it. The only difference was that they had pots which could be adjusted for stability and other features to smooth out recovery and governor surging under load.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
William1
Contributor
Contributor
Posts: 28
Joined: Sat Feb 20, 2021 10:47 am

I just did some more testing. First, I popped the stepper swivel joint off the carb. Put my meter on it in Frequency. Plugged in the blow dryer and did some tests.

Blow dryer off, idle control engaged, generator running, held at idle. Stepper motor tried to open the throttle when the blow dryer was turn on, so it senses the load. If I move the throttle manually to about 60hz, the stepper followed but at steady throttle the stepper still moved back and forth.
Turned off the idle control, blow dryer off. The stepper motor tried to open the throttle. I manually opened the throttle to 60hz. The stepper motor held position. When I turned on the blow dryer, trying to keep the frequency at about 60, the stepper motor was 'hunting' again.

With the load on, stepper linkage unsnapped, and manually trying to hold 60Hz, the stepper motor reacted significantly to any slight frequency variation. 59.5Hz and it wanted to open the throttle, 60.5Hz and it wanted to close the throttle. So during normal operation, it appears that it is constantly going to 'miss the mark' over and under shooting. In electronics, we call it 'smoothing' and this unit seems to not have that. A bad capacitor (or solder joint) on the control board could be the culprit.
William1
Contributor
Contributor
Posts: 28
Joined: Sat Feb 20, 2021 10:47 am

I just went out to put the linkage back on and noticed the threaded part was bent! I do not recall it looking bent before, so I am wondering if the stepper bent it during my tests fighting to change throttle positions. If it is not supposed to be bent, I'll straighten it (hopefully not breaking the all-thread). It does look 'intentional' as there is a slight notch right at the bend.
Chris
Site Admin
Site Admin
Posts: 3536
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

The linkage is supposed to have a bend in it, so that's normal. The stepper doesn't have that kind of force behind it.

It's hard to tell how the stepper would react when you slow it down manually, because the reactions are instant so that it can hold the throttle steady. Manually moving it will certainly cause the stepper to act funny I would think.

The best way to be able to test is to unplug the stepper like I mentioned, that way you can position the throttle and it will stay there from the friction of the stepper.

A picture of that linkage can be seen here: https://shop.gentekpower.com/products/g ... inkage-rod
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
William1
Contributor
Contributor
Posts: 28
Joined: Sat Feb 20, 2021 10:47 am

Chris wrote:
Tue Feb 23, 2021 12:21 pm
The linkage is supposed to have a bend in it, so that's normal. The stepper doesn't have that kind of force behind it.

It's hard to tell how the stepper would react when you slow it down manually, because the reactions are instant so that it can hold the throttle steady. Manually moving it will certainly cause the stepper to act funny I would think.

The best way to be able to test is to unplug the stepper like I mentioned, that way you can position the throttle and it will stay there from the friction of the stepper.

A picture of that linkage can be seen here: https://shop.gentekpower.com/products/g ... inkage-rod
Yup, my link looked like that. I though it might of but... not being an expert, I was not sure.

I was/am able to hold the throttle 100% steady by hand. The 'kicker' to me was holding the throttle steady (based on frequency of the meter), engine with a load on it (blow dryer at 1500 watts, 10% of generator capacity), holding the throttle at 60hz +/- .5 Hz and seeing the stepper constantly moving wide swings. Just like in the video. Not slight incremental movement but significant ones. Over reacting.

I think I am prepared to try a new board, does that sound rational? If so, can you confirm the correct part number?
Chris
Site Admin
Site Admin
Posts: 3536
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

I think you'll have to start somewhere and based on what you've tested and explained, it does sound reasonable that the controller is 'over reacting' to the inputs from the stator sensing information.

The controller for that unit can be found here: https://shop.gentekpower.com/products/g ... controller
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
Post Reply