MEP-831a Troubleshooting

[R Racing]

I could be wrong but I thought mine was green when I had a fault?

 

[DieselAddict]

Mechanical adjustments are going to take a while and I had limited time this morning so I thought I would try a couple of things on my "surger." Realized last night that at least half of the relays that came with my 831's are 120vAC driven rather than the 24vDC called for in the techman. I replaced the suspected relays in my surging genset this morning. Fired it up and same result - uncontrolled surging. I prevented the actuator from returning all the way to the magnet to see if the magnet was pulling it in but not the case - still surged from my stopping point to full throttle. Then I realize the indicator on K12 wasnt lit. Also heard a buzzing sound from K15 - felt it buzzing as well. I'm going to pour over the diagrams to try to see why K15 would have an inconsistent circuit and why K12 isn't being energized (closed). Odd thing is that it looks like K12 is getting consistent power and K15 is showing extremely low (or likely short bursts) of + current.

Video of this morning's experiment below...

https://youtu.be/6uTuYUCtqgM

I had one that did that exact same thing. After a lot of troubleshooting it turned out to be a bad governor. You can't get them from the manufacturer. Of 4 MEP831s that I've bought 2 need governors. This is looking to be a weak point in these generators. I'm considering building a replacement from scratch.

 

[cdre]

I remember you mentioning that. I'll probably swap a known good governor to see if that's ultimately it....

I wonder if you can get these to run with a conventional mechanical governor from one of the Chinese gensets. Would burn more fuel but it would make power....

 

[cdre]

Scratch that. Everything you need governor-wise should already be there. I'm going to pull off an actuator, adjust the set up to 3,650 RPM and see if I can make electricity. Only concern is that overload protection might kick in. Not sure how the inverter will feel about higher voltage coming in with little to no load.

Bad thing is I probably won't be able to do that until next weekend.

 

[DieselAddict]

The inverter will work fine with the RPM set to 3600 and no load. I ran the first one with controller problems like that by pinning the actuator in the start position. It just makes more noise and uses more fuel.

 

[Cord]

So I'm continuing to try to find the source of my surging speed. Yesterday I disconnected the signal to the actuator and the engine ran beautifully - so the issue is upstream of there. Then I swapped a known good actuator (stable movement) with the one that is surging. The known good actuator arm did the same thing, so the problem is further upstream. (BTW, both arms showed 10 ohms of resistance - in spec). So I got brave and starting playing with controller dials. First I checked to ensure the controller was getting a steady 24v when in "run." Confirmed. Then I connected to the A and B terminals on the controller. With the engine running, I'm getting fluctuating voltage readings but between 160 and 200 which make sense based on the engine speed. Original paint marks are on the linkage hardware, so I didn't tinker with that. Realizing stability is achieved by turning the knob clockwise until unstable then back a little, I turned the stability knob fully counter clockwise which should presumably stabilize things. No change. Then gain fully counter clockwise. No change. Then I connected the multimeter to the actuator terminals. My multimeter is too slow to really show what's going on, but you can see that it's cycling between 0v and 24v. Video below showing the signal being sent to the actuator (alligator clips slipped off in the video which is why it initially showed 0).

Any thoughts on what the issue could be beyond what I've thus far troubleshot?

https://youtu.be/9clqDLwYnrQ

I have a suggestion for you, but it's a bit radical. I finally gave up on my shut down problem and adjusted the magnet. What I found was that my magnet wasn't tight. I'm not sure if the guy who was trying to wreck my unit loosened the magnet or it was loose from the factory, but it certainly wasn't tight. When adjusting the magnet, this is what I discovered:

If the magnet pull is too weak, the unit will surge. If it's super weak, the unit will surge just like yours. It seems as if the actuator wants a little pull on it to help balance it. Too little pull and the actuator can't control it's movements.

If the magnet pull is too strong, the unit will surge, but slower and with a greater rpm range. What happens is that the magnet sticks to the target and starts to shut the engine down. The actuator then needs to pop the target off the magnet and it goes WFO for a moment. The actuator then over compensates and it sticks to the magnet again.

By adjusting the magnet with my fingers, over several days of use I was able to find the perfect magnetic balance. Enough pull that the target will stick for shut down, but not so much that the actuator sticks when a load is dropped. It's a super fine line between the two, but the unit does seem to prefer a stronger pull to a weaker one. When you are trying to set the magnet, don't bother using a wrench on the nut. Just make it finger tight. Sadly there is no way to hold the magnet still when tightening the nut and inevitably you'll change the setting.

 

[Cord]

I have one with a bad alternator. Finding that at an affordable price isn't going to happen. I can only hope that I can find a company to rewind it.

There is a guy on Ebay right now that is selling some MEP-831a parts. I've contacted him and he's been very helpful and friendly. Gave me a quote for a few parts and they should be here in a few days. I know from talking to the guy that he has several parts units so I'd suggest trying to contact him.

 

[DieselAddict]

Thanks for the heads up. I picked up one with a bad motor. I should be able to put together one more good running machine out of what I have now.

 

[DieselAddict]

I have a speed controller prototyped and working on the bench. Soon I'll be able to get the 831 that has been languishing without a good controller going. I've not wanted to sell it unless it was perfect. It will soon be better than stock. This new controller is going to work great. It has some features that the original one didn't have.

 

[OverkillTASF]

My MEP-831A's:

54-575g

• Circuit interrupter always closed - FIXED, thanks to explanation from kloppk.
• Voltage adjust ineffective, though effects engine revving a little bit - Haven't tested pot, this is on back burner for now.
• Positive battery wire ring is toast from loose connection arcing - FIX IDENTIFIED
• Speed controller linkage out of adjustment - Back burner for now
• Overload light lit
  • Overload indicator even with L1, N, L2 disconnected from A8.
  • I still get AC voltage output (though not enough voltage, but possibly due to engine speed adjustment) with light lit.
  • Opening or closing the voltage selector door doesn't seem to change voltage output.
  • It doesn't cause or attempt to shut down engine.
  • Will throw a 60 watt bulb in there to warm up the compartment and see if it's a moisture issue, per suggestion from Guyfang.

54-241g

• Positive battery wire ring is toast from loose connection arcing - Will replace
• No power at convenience outlet, GFI constantly tripped. - FIX IDENTIFIED
  
  • GFI tested as faulty, trips even outside of the MEP with no load as soon as my home power is applied.
  • Either removing convenience outlet entirely, replacing GFI/circuit breaker with equivalent units, or replacing with GFI module from another MEP.
• AC interrupter light broken - Replaced with light from another unit for now.
  • Gone, snapped off. Is there a common direct replacement? Replacement unit ain't cheap, $40; Looking at other equivalent indicator lights on Mouser/Digikey.

 

[Cord]

I've found that if you flip the voltage selector switch open and then run the unit for 1/2 hour that it's enough heat to dry the moisture out. Shut the unit down before closing the cover. My unit seems to pretty sensitive to moisture and I need to do this fairly frequently.

 

[Guyfang]

My MEP-831A's:

5
54-241g

• Positive battery wire ring is toast from loose connection arcing - Will replace
• No power at convenience outlet, GFI constantly tripped.
  
  • Problem isn't outlet, guessing it's GFI module. Direct replacement is probably stupid expensive. Seems easy enough to replace with a GFI outlet and cover from Lowes. Probably should add a 10 amp breaker. Anyone find the best solution for this?
  • Need to determine how to test GFI module.
• AC interrupter light broken
  • Gone, snapped off. Is there a common direct replacement?

Overkill, I know this going to sound stupid. BUT I had to once drive 340 klicks, one way, because someone didn't see the GFCI reset button on the side of the GFI housing. Soooooooooo, I will ask a stupid question. You do know its there and have reset it? Also, If you have a Ground fault in the set, it will not reset, while running. The GFI is easy to test. I would remove it from the set. Connect 110 volts to the input side, and press the reset, then see if you have 110 volts on the output. Can't get any simpler then that.

Follow the wires from the GFI, to the outlet, to see if there is anything damaged. I several times found a GFI OUTPUT wire chafed against the control cabinet side wall. The army GFI has a built in 10 amp breaker built into it, I seem to remember.

The AC interrupt light socket is a VERY commonly used part. Like on about ten million different types of equipment. I would assume, (in WOCC I learned that assuming will almost always get me into trouble almost every time) it should be very easy to find on the market, or from someone who is scrapping junk equipment.

 

[Guyfang]

I have a speed controller prototyped and working on the bench. Soon I'll be able to get the 831 that has been languishing without a good controller going. I've not wanted to sell it unless it was perfect. It will soon be better than stock. This new controller is going to work great. It has some features that the original one didn't have.


Chris, you are incredible. Simply incredible. If you are not rich, you should be.

 

[OverkillTASF]

Overkill, I know this going to sound stupid. BUT I had to once drive 340 klicks, one way, because someone didn't see the GFCI reset button on the side of the GFI housing. Soooooooooo, I will ask a stupid question. You do know its there and have reset it? Also, If you have a Ground fault in the set, it will not reset, while running. The GFI is easy to test. I would remove it from the set. Connect 110 volts to the input side, and press the reset, then see if you have 110 volts on the output. Can't get any simpler then that.

You're talking to someone who accidentally bought 4 generators. It's safe to assume I may occasionally do stupid things. Yes, I was aware of the reset and test buttons. Thinking the GFI really only detected ground issues on the LOAD side, and assuming that it did that by detecting an imbalance of current flow on the neutral wires, I disconnected the outlet... it still trips once the generator starts. After your email, thinking I was perhaps wrong, I did take the whole module out, wired it in a very unsafe fashion into a broken extension cord, and even with no load it once again trips as soon as power is applied. That means it's bad, right?

The AC interrupt light socket is a VERY commonly used part. Like on about ten million different types of equipment. I would assume, (in WOCC I learned that assuming will almost always get me into trouble almost every time) it should be very easy to find on the market, or from someone who is scrapping junk equipment.

Was hoping it was something I could find on Mouser or equivalent, but I'm not smart enough to know what I'm looking for. This is my first piece of military equipment so if there's a commonly used place for such parts, I don't know where it is!

I've found that if you flip the voltage selector switch open and then run the unit for 1/2 hour that it's enough heat to dry the moisture out. Shut the unit down before closing the cover. My unit seems to pretty sensitive to moisture and I need to do this fairly frequently

It's raining here today so I haven't gotten to give that generator a shot, but I don't think my neighbors will be cool with me running that for that long. Curious though, why flip the little door up? Also, your moisture issues... are they dependent on rain, or do you just have issues after the generator has sat for a while, even out of the rain? Curious because when I sell these I want to make sure I'm thoroughly accurate in what to warn the buyer about.

 

[Cord]

I store my generator at my cabin up north in a garage. The floor doesn't have plastic under the gravel so it's a slightly damp in there. I've also noticed that if the generator sits out over night in the rain it will get a bit damp inside. Not wet, just a little damp. Well, the overload circuit must be very sensitive to moisture. When the generator is damp the unit will start up fine, but a few seconds later the overload light will come on. If you try to reset it, the whole unit will shut down. The solution is to open the voltage selector door. This disconnects the over load circuit so the engine can run and dry out the interior. It doesn't take long to dry out, but you do have to be patient. If it's hot out, the unit could overheat because the fans also will not run. Gotta be careful, but the trick does work.

On EBay there was a guy from Florida selling 831 parts. His prices are very good, he's responsive and he's willing to spend time to help you diagnose a problem. I'd suggest turning to him for your gfi unit.

Be careful with the gauges. It's very easy to over tighten the nuts holding the gauge on. When over tightened, the gauge housing will crack; thus ruining it. I've had luck with putting a second nut under the mounting bracket so the second nut feels tight without straining the gauge housing. Some of these gauges are really hard to find, so be careful with the ones you have.

 

[OverkillTASF]

I get an Overload/Short light even if the voltage selector door is open. Is it at all likely that that the overload relay is bad or something? I'm considering opening up the frequency converter (not with any power applied of course).

 

[Guyfang]

Yep you need a new GFI. A lot of folks think it protects them on the output load terminals. Wrongo. ONLY at the 110 volt outlet.

The press to test light should be available. Three pin socket. Go to the below listed link and order one, or do as I did. Plug in the part number to your search engine and google it!

https://www.ecasinc.com/parts/number/MS25041-5

Also a thought. The A-2, Fault Indicator Module could be the problem concerning the overload/short circuit light being on the whole time. I have changed several of the A-2's for similar problems. If you bought 4 of the sets, do a "controlled substitution". Swap out the parts to see if that's the problem.

 

[Cord]

It's easy to isolate the Gfi by disconnecting and then taping off the hot wire. With the door open I'm pretty sure the overload light will be on.

 

[Guyfang]

All you need to do is disconnect the GFI wires at the TB, terminal board, safer that way. But the GFI has nothing to do with the overload light being on. In fact, the 400 hertz model, MEP-812A has no 110 outlet, nor a GFI. The more I think about it, the more I would look for the problem in the A-2.

 

[OverkillTASF]

Updated my list... The GFI and overload issues were on two different MEPs.

54-575g

• Circuit interrupter always closed - FIXED, thanks to explanation from kloppk.
• Voltage adjust ineffective, though effects engine revving a little bit - Haven't tested pot, this is on back burner for now.
• Positive battery wire ring is toast from loose connection arcing - FIX IDENTIFIED
• Speed controller linkage out of adjustment - Back burner for now
• Overload light lit
  • Overload indicator even with L1, N, L2 disconnected from A8.
  • I still get AC voltage output (though not enough voltage, but possibly due to engine speed adjustment) with light lit.
  • Opening or closing the voltage selector door doesn't seem to change voltage output.
  • It doesn't cause or attempt to shut down engine.
  • Will throw a 60 watt bulb in there to warm up the compartment and see if it's a moisture issue, per suggestion from Guyfang.

54-241g

• Positive battery wire ring is toast from loose connection arcing - Will replace
• No power at convenience outlet, GFI constantly tripped. - FIX IDENTIFIED
  
  • GFI tested as faulty, trips even outside of the MEP with no load as soon as my home power is applied.
  • Either removing convenience outlet entirely, replacing GFI/circuit breaker with equivalent units, or replacing with GFI module from another MEP.
• AC interrupter light broken - Replaced with light from another unit for now.
  • Gone, snapped off. Is there a common direct replacement? Replacement unit ain't cheap, $40; Looking at other equivalent indicator lights on Mouser/Digikey.