mep804a has no output

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gmanar15

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Hello
I am new to the site and would like to start off by saying hello.
I have a mep804a genset that runs and maybe worked fine before I turned the voltage control up. This shut the engine down and when I restart it the unit only shows output if I hold the switch in the start position.
I first tried the convenience plugs and it did not work. I have now found that the breaker behind the panel was tripped, but not until turning the voltage up and causing the unit to shut down.

My Dad does not call me son because I am Bright.

Any help would be great.
 

MtnSnow

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Have you followed the startup procedure as listed on the control panel cover? The unit will not produce output power to the convenience outlet nor the output lugs until the contactor has been "closed" (switch on the control panel called "AC Circuit Interrupter) Does it light up "green" when placed into the "closed" position? Does it light up green when you press the light cover in? (this allows you to test that light actually is capable of working). If answers are all good so far then very carefully with the AC Circuit Interrupter switch in the closed position check for voltage with a DVM (digital Volt Meter) on both sides of the contactor (it is found in the Right hand side Top most compartment when facing the control panel)

I would also highly suggest that you download the TM's (technical Manuals) for the unit.
 

gmanar15

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A/C interrupter light works. It also works when holding in the closed position but goes out when the switch is released.
 

MtnSnow

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They are not labeled per se` but the AC Contactor is under the RIGHT TOP Cover when looking at the control panel (Above the output lugs (where you put your power feed lines))
 

Guyfang

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What "Breaker" are you talking about? Do you mean the Ground fault interrupter, (GFI). TM 9-61115-643-24P, Figure 7, item 22. Is that what you are talking about?. On the side of the GFI, there is a small switch or reset when the GFI gets tripped. The GFI only trips when you have a ground fault problem. Or do you mean CB-1 breaker? Behind the control panel door.

To find the A.C. contactor,take a look at Figure 16, (output box assembly, in the TM. It shows you the contactor as item 36. There is a cover on both sides of the contactor, to prevent anything from making contact between the AC output cables. Like your hand, or a wrench. Two screws hold the cover on. Remove both covers. Start the set. Measure between all three cables on one side. Between any two cables you should get about 220 volts, as you are measuring between two phases. Any voltage? If not, Measure between the cables on the other side. Any voltage? If not, perform the same test while someone like your best friend, holds the start switch up while you do the test. Remember, this thing produces electricity! So be careful. Do not drop anything metal into the works. Might light up your life!! If you have voltage on one side and not the other, the contactor is not working. May not be bad, something maybe not letting it close. Like a relay. If you have no voltage on both sides, then the Main Generator is not being excited, or not "lighting off" when it gets excition. But lets first start by testing the main AC contactor. AND FIRST, like MtnSnow wrote above, GET THE TM's!!!!!!!!!!!!!! The troubleshooting diagram in the back of the book is not bad. Are you getting any idiot lights, (Fault indicator lights) coming on at any time? We need more info.
 
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MAdams

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Sorry for the hijack but I am having a similar issue. When I start the generator I am only getting 6v from each leg, and 12v across two lugs. The voltage gauge on the panel reads the same low voltage. Turning the voltage adjust knob doesn't make a difference. This is with the ac connector open or closed. Also the hz is very low. The freq gauge hovers around the lowest reading. The engine rpm does change slightly when the hz knob is adjusted.
 

Guyfang

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The 6 volts you are getting is excition voltage.

Have you tested the magnetic pickup yet? Look for it in TM 9-6115-643-24P, figure 18, item 19. It’s located above the starter. Unplug the two spade connectors. Unscrew the mag pickup from the bellhousing. Inspect it. Is it dirty? Covered in metal filings? Oil and junk? Clean it up. Has the end been ground off? If so, toss it and start looking for another. If the end is good, screw it into the bellhousing until it hit bottom. Turn it out ¾ turn and turn the lock nut down hand tight. Get a friend to help with the next step. Use a multi-meter set on AC, (yes AC, not DC) and connect it to the spade connectors on the mag pickup. Have your friend turn the engine over using the S-10 Dead Crank switch. While the engine turns over, you want to see between 2.5 and 3 volts on the multi-meter. If it reads low, turn the mag pickup to the right. BUT JUST A TAD AT A TIME!!!!!!!! You don’t want to grind the end off. If its toooooooo high, turn the mag pickup to the left. When you have it at 2.8 or even better 3 volts AC, lock it down without moving the mag pickup. Connect the spade connectors and then start the set up and see if it now runs right.

Or you can test it this way, but I always pull the mag pickup, just to see if it is dirty or ground off. This is straight out of the TM.

2.108.4. Adjustment.
a. Release control panel by turning two fasteners and lower control panel slowly.
b. Disconnect wire 147C from terminal 16 and wire 148C from terminal 17 of governor control Unit.
c. Set multimeter for ohms and connect to ends of disconnected wires 147C and 148C. Multimeter should indicate
between 800 and 900 ohms.
d. Leave multimeter connected to wires 147C and 148C and set multimeter for AC volts.
e. Crank engine with DEAD CRANK switch and observe multimeter. Multimeter indication should be between 2.0 and
3.0 VAC.
 
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MAdams

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Ok I'm getting OL for ohms while measuring the mag pickup. I'm bring less than 1vac while using the dead crank. Any idea what the mag pickup pn# could be? Thanks for getting me this far
 

Guyfang

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Have you pulled the mag pickup? Look at it. If its not ground off, reinstall and give it a try.

This is the CAGE CODE. 05624 Its the code for the manufactures name. I am looking for an old copy of FEDLOG, and then we can look it up.

This is the Army part number. 88-21061

Proper name is: TRANSDUCER, MOTION
 

Guyfang

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6,306
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[h=1]This is what I found when I looked up the cage code.


GE AVIATION SYSTEMS LLC[/h][h=2]Cage Code 05624[/h][h=3][/h][h=3]LOVES PARK, IL, UNITED STATES[/h][h=3]
http://www.armyproperty.com/contactManufacturer/05624/GE+AVIATION+SYSTEMS+LLC[/h]































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Established: N/A
# of NSN's assigned: 5289
Phone: Login to view
CAO Code: S1403A
ADP Code: HQ0339
Status Code: A
Assoc Code: 05624
Type Code: F
Size: E
Primary Business: N
Business Type: N
Woman Owned: N
Sic Code: 3728
 

MAdams

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Ok thanks. I'll try to cross reference the numbers. I pulled it and it looks great. There were a small amount of metal shavings on the head but not too many. I bottom it out and then backed off 3/4 turn but I had the same results. I turned it in another 1/4 turn and had the same results.
 

Guyfang

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MAdams,

Its rare that a mag pickup goes bad. Thats a shame. Whenever a 804 has no volts and no freq control, the mag pickup is the first place to look.
 

Jsampo85

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blown fuse above the voltage regulator and no Hz or Voltage output shown on the panel

The 6 volts you are getting is excition voltage.

Have you tested the magnetic pickup yet? Look for it in TM 9-6115-643-24P, figure 18, item 19. It’s located above the starter. Unplug the two spade connectors. Unscrew the mag pickup from the bellhousing. Inspect it. Is it dirty? Covered in metal filings? Oil and junk? Clean it up. Has the end been ground off? If so, toss it and start looking for another. If the end is good, screw it into the bellhousing until it hit bottom. Turn it out ¾ turn and turn the lock nut down hand tight. Get a friend to help with the next step. Use a multi-meter set on AC, (yes AC, not DC) and connect it to the spade connectors on the mag pickup. Have your friend turn the engine over using the S-10 Dead Crank switch. While the engine turns over, you want to see between 2.5 and 3 volts on the multi-meter. If it reads low, turn the mag pickup to the right. BUT JUST A TAD AT A TIME!!!!!!!! You don’t want to grind the end off. If its toooooooo high, turn the mag pickup to the left. When you have it at 2.8 or even better 3 volts AC, lock it down without moving the mag pickup. Connect the spade connectors and then start the set up and see if it now runs right.

Or you can test it this way, but I always pull the mag pickup, just to see if it is dirty or ground off. This is straight out of the TM.

2.108.4. Adjustment.
a. Release control panel by turning two fasteners and lower control panel slowly.
b. Disconnect wire 147C from terminal 16 and wire 148C from terminal 17 of governor control Unit.
c. Set multimeter for ohms and connect to ends of disconnected wires 147C and 148C. Multimeter should indicate
between 800 and 900 ohms.
d. Leave multimeter connected to wires 147C and 148C and set multimeter for AC volts.
e. Crank engine with DEAD CRANK switch and observe multimeter. Multimeter indication should be between 2.0 and
3.0 VAC.
I was actually measuring my Mag pick up after removing them from the MPU #'s 16 and 17 and I read 5.88V, is that a good thing that it's above the 2.0-3.0V or could there be something that is more underlying to my problem. I have the same issue as this gentleman, after prime/Run and when I hold the switch for 2 seconds in the start position for field excitation the 3A "Limitron- Fast Acting KTK-3" bus fuse blows instantly and my Gen-Set shuts down as soon as it's released from the start position. After you reset the control switch and go back to normal start position it starts no problem, no hard starting or anything but I get NOTHING reading on my HZ gauge or my Voltage Gauge, any suggestions to what this problem could be, or have you ever encountered this before?
 

Guyfang

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The voltage produced and measured from the Mag Pickup should NOT exced 3 volts. Adjust the mag pick up as described above. If for some reason you can not adjust it down to 2.5-3.0 volts, the pickup is bad.

I assume by 3A limitron fast acting KTK-3 bus fuse, you mean the Quad circuit fuse, to protect the excitor windings. If your Volt regulator is defective, and sends to much voltage to the exciter windings, they burn up. Hence the fuse. You can measure how much voltage is going to the windings, by removing the fuse and measure from ground to the input side of the fuse holder.
 

Jsampo85

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The voltage produced and measured from the Mag Pickup should NOT exced 3 volts. Adjust the mag pick up as described above. If for some reason you can not adjust it down to 2.5-3.0 volts, the pickup is bad.

I assume by 3A limitron fast acting KTK-3 bus fuse, you mean the Quad circuit fuse, to protect the excitor windings. If your Volt regulator is defective, and sends to much voltage to the exciter windings, they burn up. Hence the fuse. You can measure how much voltage is going to the windings, by removing the fuse and measure from ground to the input side of the fuse holder.
Yes I mean the quad circuit fuse, we were able to reduce the voltage of the mag pick up by just replacing it and tuning it down to 2.6 volts. However the fuse continues to blow even though with S1 held in the start position we are only getting 3.8V AC at the topside of the fuse holder and in run 25Millivolts AC.
 

Guyfang

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The field flash voltage should be DC voltage. If you are getting AC voltage to the exciter windings, something is wrong. I would replace the volt regulator. Below is a passage from the TM.

1-12.8.2 Field Flash. When the engine reaches sufficient speed (900 rpm), the magnetic pickup causes a set of contacts
in the crank disconnect switch to close and energize the field flash relay. This circuit provides current to the
exciter field windings which sets up an electromagnetic field. The field current is necessary for the set to generate
sufficient voltage for the voltage regulator to begin controlling the output voltage of the generator set. The field flash
circuit is maintained until the MASTER SWITCH is released from the START position

​The mag pickup does NOT provide the excitation voltage, just tells the crank disconect switch to do its thing and energise the excitor with 24 volt DC.
 

Jsampo85

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ok, I will double check it again Monday morning and update you on a DC reading at the top of the fuse holder. Also when we read across pins 1 and 3 of the voltage regulator we weren't really reading anything, shouldn't that be producing voltage, from the other posts I was reading I would say YES, lol
 

Guyfang

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I would have to see what is hooked to pins 1 and 3. I am getting ready to boogie down to the Bodensee to pick up my wife. I leave in the morning, get back on tuesday.

Just looked quict. Pin one goes to through FU-2, quad fuse to the F1 on the G1, (Main Generator). Pin 3 goes to the F2 on the G1. This is the circuit that lights off the excitor windings. No voltage there, not main gen output.
 
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