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MEP 803A Overload Fault Troubleshooting

CallMeColt

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Everyone,

I know there are a few threads on this already. Have read through them & learned from them. Used that & have troubleshooted, but am still a but stumped. My situation is a little different, so I will try to consolidate what I have done as much as possible so that I can get some input here.

SITREP... My MEP 803A is a 2011 manufacture. It appears to sat inside a warehouse as it looks virtually new inside & out. The scraps/dents are from me or the state level surplus that handles it. Had 31 hours on the meter. No reset. All the extras inside seemed to never be touched. Fuel & fluid was left in it, so the floats were sticky. That was the only issue with it when I got it. Removed & cleaned the double float switch, replaced the sender, fresh fluid with some ATF, and it runs very nice. Had oil & coolant that was not to old in it already. Batteries were not old, Optima. So, mechanically it is good. I planned to run it through my 6 hour load test, then do a full filter/fluid swap & call it ready. Now, here we are.

After warming it up, loaded it to 5,000 watts with 240v electric heater. 240v single phase setting. Added the second one. Then, a 1,750 watts 110v heat gun. Then, a 1,500 watts 110v heater. One of the 240v leads had a power distribution box. It was burning off great. I suspect this generator was never even really run under load, just started to charge the batteries over the years. It barley has the paint burned off the exhaust manifold. After a few minuets, walked away to come back out & see the overload. Was a bit surprised as it seemed to be fine, but figured maybe it was due to one leg being loaded. Not the case. Basically, even with the even 10,000 watts, it will overload. With battle short on, it will go all day. With the S6 in a position for 3 phase, it will go all day.

Here is what I did for troubleshooting.

Used CRC contact cleaner liberally on S6 & S8. They appear perfectly clean, but figured I would. I know the forum recommends the DetoxIT, so I have some on the way.

EDIT: Forgot to put that I swapped the S14 for a known good. No change.

Checked loops on the CT. All are good. 4.

Checked connections on S6. Found some of my wires 6's have 8's, but they otherwise match up at the other end. Same on S8. For example, 187A should be 167A. Error from the manufacturer.

Disconnected J6 & J7. Both are tight & clean. Bright gold. No green.

Check tightness on all connections. Overall, I did find a lot of things I'd say were loose on this generator. Biggest hint to this was a single TB screw in the bottom of the generator. I was really hoping this was going to be my gremlin, but it wasn't. It was from TB4-7 that is blank. But, TB4 had fallen off the generator and was just loose!! Secured that. Was hoping THAT would be my issue, but no. Found a loose connection due to a semi stripped screw on K8-6. Replaced it. No change by tightening connections on just about all connections involved.

405.jpeg

Used my multimeter and a Kill A Watt to calibrate the gauges. The frequency & voltage were off a bit. Wasn't sure if this could contribute. Set to 60hz and 240v exactly then adjusted the gauges.

I replaced R11 with a known good. I know they should all be de-soldered to be checked. I didn't do this yet to them all but when checking against other units I have, this one gave me a rather off ohms reading so I did it. After it being removed, it read fine. So, don't do this.

In one of the posts, I found @kloppk Post the proper voltages for R10, R11, & R12. Here is where I'm seeing issue.

R10 0%-1.3v 50%-2.1v 100%-4.3v 115%-5v
R11 0%-1.3v 50%-2.1v 100%-4.3v 115%-5v
R12 0%-1.4v 50%-4.2v 100%-9.5v 115%-9.5v

I know at 0%, it should be 0v. But, I think the big issue is on that R12. That imbalance is there. So, using this schematic I got from another post, I looked more in depth on that leg.

1713358123028.png

The CT produces the voltage to these, so I started there. It goes through CT3. I have wires 003A10 & 009A10 in there looped 4 times. Removed the C1 & C3. Has continuity. Cleaned everything & attached. At the point I am at when typing this, I need to let my CRC contact cleaner dry before trying to run again after cleaning.

I took out my hardback TM with the wire diagrams and went through everything on that leg. WOW, it's a lot. I have the older style switches, so it should match perfectly the diagram with the numbers. I used the diagram from above, printed it, and started doodling to fill the details in. Here is is;

393.jpeg

As I'm typing this, my next step is to go touch & check each wire in that leg. At this point, I suspect a bad CT or something in the plug side of J6/J7. Before I start going wild with ripping major stuff out & throwing parts at it, I wanted to see if I am missing something obvious since I'm kind of in deep & a bit frustrated. Been at this almost two days now when I expected to be giving this the okay & having the trailer setup again & on to better things yesterday afternoon. If I think of something I did & didn't put in this post, I will come back to edit.

Just a few pictures to show how clean it is;

image000004.jpg.jpeg image000002.jpg.jpeg image000001.jpg.jpeg image000000.jpg.jpeg image000006.jpg.jpeg
 
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WWRD99

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I'm a little confused on one thing, is when you set it for 3 phase the genset works fine powering the stove and other things, or do you have a 3 phase load bank. I can't remember since you have a bunch of stuff I've seen on your videos. That could point in a direction to go if 3 works but single is not...one leg might be weak. Can you test it full load on just 120 not 240? I know that's a big one but might isolate it some. Sounds like you've run through the contacts and wiring pretty good.

Sent from my SM-S906U using Tapatalk
 

CallMeColt

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I'm a little confused on one thing, is when you set it for 3 phase the genset works fine powering the stove and other things, or do you have a 3 phase load bank. I can't remember since you have a bunch of stuff I've seen on your videos. That could point in a direction to go if 3 works but single is not...one leg might be weak. Can you test it full load on just 120 not 240? I know that's a big one but might isolate it some. Sounds like you've run through the contacts and wiring pretty good.

Sent from my SM-S906U using Tapatalk
The load has nothing to do with it. It is a fault in the way it is sensing. The generator is working fine.

If you set S6 for 3 phase, it is monitoring for such, it is not setting the generator to make 3 phase power. You set the way the generator makes power with S8. You set how the generator monitors power with S6. What I was getting at is if you trick the generator into not monitoring properly, the fault won't show up.
 

WWRD99

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The load has nothing to do with it. It is a fault in the way it is sensing. The generator is working fine.

If you set S6 for 3 phase, it is monitoring for such, it is not setting the generator to make 3 phase power. You set the way the generator makes power with S8. You set how the generator monitors power with S6. What I was getting at is if you trick the generator into not monitoring properly, the fault won't show up.
Ohhh ok I got the s6 and s8 mixed up!

Sent from my SM-S906U using Tapatalk
 

CallMeColt

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Added a few things to my original post that I forgot to put in there.

Also, After letting the contact cleaner dry & touching/tracing each wire to confirm it is in the proper place, no luck. I also unbolted to CT to make sure I could get a good look at the side of the S8 & some of those connections I got a little tighter. In the end, everything is exactly as it was to start with.

It seems like I can't get a one of these that doesn't end up turning into a neck-deep project. Even if it is brand new looking. :cool:
 
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CallMeColt

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You indicated you had 9.5 v across R12. What's the voltage across R13?
When set to 120/240 the switch connects R12 and R13 in parallel. My hunch is they are not getting connected in parsllel resulting in about 2x the voltage.
I did not take a measurement of R13. Good catch. Your diagram shows this & I kind of ignored it for some reason.

I will have to pull the trailer back up to the shop & set the load bank up again to test. This afternoon I moved onto my M4K with about the same results as the generator. Should have just sat in the chair & enjoyed the weather this weekend!

What should I be expecting to read across R13 at 100%? I did already, but I will check the wires/switches again related to R13 as well.

This unit & the M4K are my priority projects as of right now, so I will try to get to it ASAP & report back.

Thanks for the input.
 

CallMeColt

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At 100% both R12 and R13 should have the same voltage of about 5 volts like the other resistors.
Okay, thank you.

I don't know why I didn't check it. I must have read incorrectly in another post where you talked about this and thought only the first 3 were for each leg. This is what happens when brain fatigue sets in!
 

CallMeColt

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@kloppk R13 & R12 are getting the same, elevated voltage readings as I posted above.

So, this is making me think there is an issue with the CT or the wire trail going through CT3 that is making the CT read higher?

If I recall, the TM test for the CT in the machine is a simple continuity test & I've done that. The next is to remove it & wind wires that are hooked to a transformer & put known voltage/amperes through it to check for proper readings. I don't have a way to do this.

Possible that SOMETHING is still dirty, but I'm doubting this. None the less, my Detoxit 5 arrived. Since it just ran, going to let things cool & soak the S6 & S8 again. Then, let it dry.

I also might try my trusty mallet & some persuasive hits. This has done it's magic in the past.
 

kloppk

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It could be one of the resistors has failed open. I'd suggest disconnecting the two wires to CT3 and then measure the resistance between the two removed wires. It ought to be 3.75 ohms. The resistance of R12 & R13 7.5ohm resistors in parallel. If you get about 7.5 ohms then I'd suspect one of the resistors has failed.
 

CallMeColt

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It could be one of the resistors has failed open. I'd suggest disconnecting the two wires to CT3 and then measure the resistance between the two removed wires. It ought to be 3.75 ohms. The resistance of R12 & R13 7.5ohm resistors in parallel. If you get about 7.5 ohms then I'd suspect one of the resistors has failed.
Did this just now & got ~7.8 ohms. So, something is keeping them from parallel between CT1/2 & the resistors or one is bad. Looks like I know where to dig into next. Thank you!
 

CallMeColt

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So, took me a bit to come back! Over the weekend I went to do my standard 6 hour load bank test & it failed. Had to work through some mechanical issues.

Had the day off to go pickup an auction win & seems like it will pass today. At ~5hrs, 12,000 watt load.

Needless to say, the issue this thread was started for has indeed been fixed. As always, I learned & greatly appreciate the help!

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