MEP-804a K1 Contactor Issues

[mrbeef]

I purchased this MEP-804a back in early 2020 and it has worked flawlessly. PO used it to power a trash compactor and I've used it to power a couple pieces of 3 ph equipment. Since I wasn't using anywhere close to its capacity, I was lucky enough to find a load bank to load up the unit and put it through its paces every 3-6 months. I last powered it up in late July and exercised it for about 45 minutes. I took it out the other day to work it some. Start up went normal, voltages showed 120 and 208 in the proper lines and 60 hz, closed the AC Interrupter and nothing. No faults were indicated.

By no means do I have any experience with electrical components, but I can read and learn. In my initial observation I noticed that the K17 relay wasn't behaving right, I have read through the technical manual and found lots of good information on here. Nothing in the technical manual directly fits my issues (as best I can tell). I've tested several components and they have all tested good so far. I have centered on K1, when I close the circuit, the contactors close but wont stay closed. I do have 120v to each leg going to the contactor from the gen head but no power on the other side. I have not tested for the 24v to close the contactor yet, ran out of time this evening to work on it. Based on my research so far I have a couple questions/comments:

1) I've noticed several mentions of K1 collecting water and rusting. This unit is not stored outside. The contactor doesn't seem stiff and does move freely, Are there any other known issues with these contactors? or additional testing I could do.

2) Any suggestions on where I might look if there this a voltage issue going to the contactor? I did swap K17 and K15 with each other just to check and no change.

3) I did try the suggested test of S1 in the run position, S7 (battle short up), and close the contactor and nothing. With the unit running the contactor will close but reopen as soon as the momentary switch is released.

 

[Ray70]

Not sure if the 804 is the same as an 802/803 but I had an 803 doing the exact same thing and the problem ended up being the short circuit / overload relay being defective.
Contactor would close as long as I held the switch, but opened when switch was released.
The TM should explain how to easily test K1 and the associated wiring. In my case K1 and wiring tested good so I swapped out the relay and it was good to go. If this turns out to be your issue, I believe Light in the Dark has new overload relays available.

 

[kloppk]

Be sure the diode CR3 is installed on S5 is in the correct orientation and that the diode is good for starters.
The CR3 diode is sometimes removed or mis-installed.

To see if K8, S5 or the CR3 diode may be the issue you could do the following.
Start the set and then measure the DC voltage at:
1) S5-5, S5-2 & S5-3 with respect to chassis ground. All should have ~24 volts DC on them.
1) K8 terminals 7,8,9 & 10 with respect to chassis ground. All should have ~24 volts DC on them.
2) K1-11 should have ~24 volts on it with respect to chassis ground.

 

[Guyfang]

You do not get any idiot lights?

 

[mrbeef]

Thank you everyone for the suggestions and ideas. I will work through those in the next few days. Couple of things we have done so far (I had a friend walk me through a couple test that he wanted to do based on the wiring diagram). We have tested for continuity on the overload relay and tested good. I do need to do some further tests with the unit running on the overload (I dont have my notes with me or I would list that out but I know it has something to do with the overload relay).

Kloppk I will work through that list of tests as well and report back.

I have been very happy with the service this unit has provided me to date and for how quiet it is and the quality of the power it puts out its hard to think about not having it. So figured with that frame of mind, I need to learn more about the electrical components so I can diagnosis and repair it.

You do not get any idiot lights?

No lights on the board. They all light up when tested but nothing when running. Between that and having ~125V per leg at K1 tells me that its something "simple" and easy to fix once I can diagnosis it successfully.

 

[Ray70]

By "having 125v per leg at K1" I assume you mean on the input side coming from the AC select switch?
If so, have you functionally tested the K1 relay per the TM?
I see you checked continuity on the wiring, but the TM should tell you how to run a jumper from battery +24 to the contactor and a ground wire to manually close K1 ( with the set off )
Myself and others here have all seen issues where K1 looks great and seems to work fine when you remove the cover, but needed a few swift whacks from the " "BFH" ( AKA rubber mallet ) to get it to close ( in an emergency situation )
Before you go any further, make sure K1 is in fact working correctly when you apply 24V to the appropriate terminals, and also ensure applying the 24V also gives you continuity across the other 2 small terminals to illuminate the green indicator light.

 

[mrbeef]

By "having 125v per leg at K1" I assume you mean on the input side coming from the AC select switch?
If so, have you functionally tested the K1 relay per the TM?
I see you checked continuity on the wiring, but the TM should tell you how to run a jumper from battery +24 to the contactor and a ground wire to manually close K1 ( with the set off )
Myself and others here have all seen issues where K1 looks great and seems to work fine when you remove the cover, but needed a few swift whacks from the " "BFH" ( AKA rubber mallet ) to get it to close ( in an emergency situation )
Before you go any further, make sure K1 is in fact working correctly when you apply 24V to the appropriate terminals, and also ensure applying the 24V also gives you continuity across the other 2 small terminals to illuminate the green indicator light.

Good news, the MEP-804A is working once again! Thanks to everyone for their suggestions and help.

After digging through more of the technical manual and more testing I determined that B1 and B2 on K1 had no continuity when the contactor was manually pushed closed. I pulled the whole assembly out of the generator and proceeded to disassemble and test all components for good measure. I tested the contactor using 24V and it worked fine but there was a clear gap between the contactor and bus bar (maybe that is not the right term). Further disassembly found some wear marks on the side of the assembly most likely caused by some oxidation and/or other debris. Cleaned the whole assemble, tested and everything seemed to work well. Reassembled the contactor and reinstalled in the generator. Should have made a video of the cold start, the gen set was very angry at 10 degrees, got it warmed up and closed the interupter and boom a nice green light. Test show 59.6 hz and 120.4V at the output lugs.

Tomorrow I will get the load bank out and let it run for an hour or so at load for its regular exercise. Too cold tonight to do that.

Hopefully this will help anyone researching in the future.

Following disassembly


Wear shown on the contactor assembly causes by debris and oxidation within the magnet.


Producing power again.

 

[Ray70]

Sweet deal! back in action with essentially Zero dollars spent on parts! Perfect!

 

[mrbeef]

Sweet deal! back in action with essentially Zero dollars spent on parts! Perfect!

Best kind of repair. Learn a little bit and pay zero tuition dollars for the education. That is a lot better than most of my "projects".

Ran it on the load bank for about 45 minutes tonight and ran great. It was running a little warmer than I expected/remember (ambient temp was ~25F) but it held steady and then when I removed the load it cooled back down to ~175-180. This Spring I might look into that a little more, clean the radiator, check the coolant, fan belt, etc.

 

[Guyfang]

Meters are to be taken with a grain of salt. I would check it with a more accurate means first.

 

[mrbeef]

I wanted to circle back on the last comment of the temp gauge issue back in December (in case someone is doing a search in the future and finds this thread). Got the 804A out last weekend to exercise it a bit since I last ran it in Dec when I posted this. Happy to report the contactor worked perfectly. Set the unit up to run for an hour or so. I was working about 300 ft away and I heard the gen stop. Not good, walk out an the "coolant high temp" warning light illuminated. Hmmmmm. Opened all the doors to try and get some cool air in there, it was clearly HOT. Nothing outwardly wrong with the cooling system. Got it restarted to see if there was a fan or belt issue that wasn't visually apparent. Quickly ID'ed the issue, loose fan belt. I pressed on the belt during my visual inspection but I think the heat of the engine really distracted me. Got the belt tightened up and the unit cooled right down. Let it run unloaded for a bit, loaded it up to 15 kw and babysat it for about 30 minutes and then let it run for an additional 30 minutes. No issues. I do need to replace the belt the next time I get the unit out since it is now adjusted to the outer limit of adjustment.

And since we all like pictures, I did take one. Happy to have this unit if/when I ever need it. In May we had a derecho go through and a lot of local cities lost power for more than 24 hrs. We didn't have any damage and were not home to loan out the generator on a trailer to friends or family. Here to the next exercise date ~Oct/Nov.

 

[Guyfang]

Good to hear. Lots of folks do not close the loop, and we dont really learn from a thread. Thanks.

how far are you from Hill City?

 

[mrbeef]

Good to hear. Lots of folks do not close the loop, and we dont really learn from a thread. Thanks.

how far are you from Hill City?

Yes, closing the loop, even 6-12 months after the fact is important to me. Being a moderator on other forums and FB groups has taught me that there are a lot of requests for technical help and then no follow up to know which suggestions worked or how the problem was solved.

We are clear on the other side of the state! (about a mile from the SD/MN state line). We were over in Hill City early last week on a vacation, it was HOT!

 

[Guyfang]

The last two times we came over to the States, while in Hill City, I had to evac my family, due to major Forest Fires. The Hills doesn't need anymore fires. The summer temps when I was a kid, there, were WAY lower. The Hills, Heaven on Earth.