MEP-804A Under voltage light

[Pain]

Greetings all!

I am looking for some help with fixing a MEP-804A genset that's been a real trouble for the past several weeks.

For starters it will turn over and run, however after you release the master switch from the start position, the "under voltage" fault lamp will illuminate. This will remain lit until the generator is turned off. If you adjust the voltage or frequency dials, little changes aside from the Hertz, of which will stay below 50 on the respective gauge. Moving the voltage dial causes nothing to change the reading/output, and it hovers around 12-16 volts. The only way to get the gauges to show something close to the normal range/ expected readings is upon startup while holding the master switch in start.

Some interesting notes I can include:

The gauges themselves for the Voltage and Frequency (Hz) readings work fine, and I've done testing on them according to the manuals I have on hand here. I can always check them again, however.

The AC Circut interruptor switch will not remain closed, it will however light the indicator light if you hold the switch yourself.

Another finding I had was when I connected a piece of diagnostic equipment to the testing port, it causes the "under voltage" lamp to go away after starting it up, and instead now causes the "over voltage" lamp to illuminate. The generator will also shut itself down immediately in this condition, unless you hold the master switch in the start position, but when you let go of it will shut down once again. This condition only occurs when you have the diagnostic piece plugged into the port. Once you remove it and restart the generator, the "under voltage" scenario I mentioned earlier will come back, the "over voltage" lamp will not light, and the generator once again will continue to run once the start switch is let go of.

I will provide all the information I can on the piece of equipment that is requested to help things along, if anyone has any idea as to what is going on with it.

For now I can report that I have replaced the master switch, voltage regulator, the K17 relay, and voltage dial potentiometer. All of which have not changed anything The electronic components all are made by TRC, as I know that mixing from the other company can cause a myriad of problems. I have visibly inspected the wiring harnesses and cannot find any chafed or broken/exposed wires. At one point I held the AC circuit interrupter switch closed and checked the output terminals, where I got a reading of roughly 15 volts.

I have been through the manuals on so many occasions that I am running out of ideas on what to continue testing/troubleshooting unfortunately. I am still new to working on generators, and this community and it's posts have been a phenomenal source of learning and help. I can hope to hear from some of you if you have any ideas/something to try out!

Many thanks for reading, and any help is appreciated.

 

[Guyfang]

Greetings all!

I am looking for some help with fixing a MEP-804A genset that's been a real trouble for the past several weeks.

For starters it will turn over and run, however after you release the master switch from the start position, the "under voltage" fault lamp will illuminate. (This is because the AC volt regulator will not take over control of AC voltage.) This will remain lit until the generator is turned off. (That is normal.) If you adjust the voltage or frequency dials, little changes aside from the Hertz, of which will stay below 50 on the respective gauge. (The AC voltage will not change, as none is being produced. The Hertz will not change, as the Frequency Transducer has no AC voltage to convert and display on the meter.) Moving the voltage dial causes nothing to change the reading/output, and it hovers around 12-16 volts. (This is inductive voltage) The only way to get the gauges to show something close to the normal range/ expected readings is upon startup while holding the master switch, (S1) in start. (When you do this, you excite the Main Gen, and it will produce AC voltage, as long as S1 is held up. You do NOT want to hold the S1 in the start position for long time periods!!)

Some interesting notes I can include:

The gauges themselves for the Voltage and Frequency (Hz) readings work fine, and I've done testing on them according to the manuals I have on hand here. I can always check them again, however. (No need)

The S5, (AC Circuit interrupter switch) will not remain closed, (K1) it will however light the indicator light if you hold the switch yourself. (Normal. The K1 , output circuit breaker is being told to not stay closed because there is no AC voltage being produced. Holding up the S5, keeps the K1 closed, and keeps the DS7, (AC output Indicator light) on, until you let S5 go.

Another finding I had was when I connected a piece of diagnostic equipment (What equipment?) to the testing port, (What pins?) it causes the "under voltage" lamp to go away after starting it up, and instead now causes the "over voltage" lamp to illuminate. The generator will also shut itself down immediately in this condition, (Normal, you are triggering the over voltage function, in the Fault indicator, and the set shuts down.) unless you hold the master switch in the start position, (Bypassing all the gen set safety circuits) but when you let go of it will shut down once again. (The safety circuits are no longer bypassed, so it shuts down) This condition only occurs when you have the diagnostic piece plugged into the port. Once you remove it and restart the generator, the "under voltage" scenario I mentioned earlier will come back, the "over voltage" lamp will not light, and the generator once again will continue to run once the start switch is let go of.

I will provide all the information I can on the piece of equipment that is requested to help things along, if anyone has any idea as to what is going on with it.

For now I can report that I have replaced the master switch, voltage regulator, the K17 relay, and voltage dial potentiometer. (What you need to do is stop throwing money at the set, and trouble shoot.) All of which have not changed anything The electronic components all are made by TRC, as I know that mixing from the other company can cause a myriad of problems. I have visibly inspected the wiring harnesses and cannot find any chafed or broken/exposed wires. At one point I held the AC circuit interrupter switch closed and checked the output terminals, where I got a reading of roughly 15 volts. (You are going to ruin the set if you keep doing that)

I have been through the manuals on so many occasions that I am running out of ideas on what to continue testing/troubleshooting unfortunately. I am still new to working on generators, and this community and it's posts have been a phenomenal source of learning and help. I can hope to hear from some of you if you have any ideas/something to try out!

Many thanks for reading, and any help is appreciated.

First step. Do you have the quad circuit modification on the gen set? Looks like the item circled in the picture. It has a big honking fuse in it. If you have it, pull the fuse and see if it is good, with a multimeter set on ohms. If its blown, do not jump the fuse. Bad things might happen. Get another fuse, JUST like it. Get two. Its there to keep a bad AC volt regulator from destroying your main gen.

 

[Pain]

First step. Do you have the quad circuit modification on the gen set? Looks like the item circled in the picture. It has a big honking fuse in it. If you have it, pull the fuse and see if it is good, with a multimeter set on ohms. If its blown, do not jump the fuse. Bad things might happen. Get another fuse, JUST like it. Get two. Its there to keep a bad AC volt regulator from destroying your main gen.
[/QUOTE]

Yes that fuse is there. It seems bad as I get an "OL" reading on my multimeter. Do you happen to know what kind of fuse it is? The markings are quite faded making it hard to get an idea of the manufacturer/ what it's rated for.

The diagnostic equipment I tried hooking up is a piece off the WATS kit, I'll attach some pictures for reference. All the pins connect to it.

 

[kloppk]

The fuse is a KTK-3

 

[kloppk]

The fuse is on the output side of the voltage regulator. After replacing the fuse and before starting it I'd suggest checking the Static Exciter resistance using it's 2 connections to the VR to be sure the resistance is in spec and that there isn't any continuity from either lead to chassis ground.

 

[Guyfang]

What ever a WATS kit is, I have never heard anything about it. The military did not buy any test equipment for power generation. So what ever info you have about it, I would like to see. But plugging it in, might not be a good idea until you know its made to test a gen set.

 

[peapvp]

First step. Do you have the quad circuit modification on the gen set? Looks like the item circled in the picture. It has a big honking fuse in it. If you have it, pull the fuse and see if it is good, with a multimeter set on ohms. If its blown, do not jump the fuse. Bad things might happen. Get another fuse, JUST like it. Get two. Its there to keep a bad AC volt regulator from destroying your main gen.

Yes that fuse is there. It seems bad as I get an "OL" reading on my multimeter. Do you happen to know what kind of fuse it is? The markings are quite faded making it hard to get an idea of the manufacturer/ what it's rated for.

The diagnostic equipment I tried hooking up is a piece off the WATS kit, I'll attach some pictures for reference. All the pins connect to it.
[/QUOTE]
Did this 13689503-101 come with your Genset?

 

[peapvp]

This devices is DEMIL Q INTG 3

Q Commerce Control List Items (CCLI) - Mutilation to the point of scrap required outside the United States. In the United States, mutilation requirement determined by the DEMIL Integrity Code. DOD Trade Security Controls (TSC) required in the United States. (Note 8 )

8.
DEMIL Code "Q". This code is specifically for Commerce Control List Items (CCLI) that are under the jurisdiction of the Bureau of Industry and Security (BIS), United States Department of Commerce, according to parts 730 through 774 of Title 15 Code of Federal Regulation and indicated on the Commerce Control List (CCL) by a five-digit Export Control Classification Number (ECCN). DEMIL code "Q" items are further categorized as sensitive or non-sensitive based on criteria established by the DDPM.
a. CCLI identified as sensitive requires mutilation inside the United States. Such property is assigned a DEMIL Integrity Code (IC) of "3" in accordance with Volume 1 of the DEMIL Manual.
b. CCLI identified as non-sensitive requires DOD TSC inside the United States according to DOD Instruction 2030.08. Such property is assigned a DEMIL IC of "6" in accordance with Volume 1 of the DEMIL Manual. CCLI with a DEMIL IC of "6" does not require mutilation prior to release within the United States.
c. Mutilation is required outside the United States and its territories for all CCL

I hope you don’t mind being waterboarded by DIA