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Thread: MEP-003a No voltage

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    Default MEP-003a No voltage

    I currently have no electricity in the house and with the spotty Internet I can get from my cell phone (that I didn't charge last night...), I don't have the ability to download a manual or large files. I need electricity to get my heat up and running right now and I'll need water when the kids get home from school.


    I have a MEP-003a that I bought many years ago from Gov Liquidation. It was marked as "Unserviceable/Unrepairable" and the reason was "No Oil." I put filters, oil, fuel, and batteries in it and it fired right up and worked as designed. I've powered my house and my parents' house with it many times. It ran my parents' whole house after Sandy for 4 days straight. At my new house out in the sticks here, I've only had to use the generator rarely. When not in use, it sits under cover in a run-in shed I have.


    I pulled it out today with the tractor, hooked up the batteries, and gave it a crank after a 1 minute pre-heat. It fired up after a few seconds of cranking and hummed along just fine. When I checked voltage, I had 0.474vAC at the convenience plug on the panel. I have that same voltage across the L1 and L0 lug and the L3 and L0 lug. Across L1 and L3, I have .759vAC. I have the selector switch set to 120/240v. At the convenience plug, I used my Fluke to read frequency and I am at 60Hz give or take a little fluctuation. I've worked the breaker back and forth several times and it's in the ON position now. The gauges on the panel all read to the far left.


    So I really don't know much about the generator's intricacies. I bought it, filled it up, and ran it. It's always worked great for me. I found something about "flashing the field" but I don't quite understand how to do that. The best I could tell from browsing through threads was that I turn the switch to "start" while it's running and that should do it. I tried that and it makes an awful noise like the starter is spinning while it's running, which I don't believe it should be doing. While I do that, the voltage at the convenience plug reads ~91vAC on the Fluke, the volt meter on the panel reads about 180vAC, and the frequency gauge on the panel is pegged at 65 Hz. When I release the start switch, the frequency drops back to the far left again, voltage on the gauge drops to the far left again, and the Fluke reads .483vAC again.



    Any help here? Again, my house is currently not being heated and I have no power. I haven't tried or tested anything other than what I've described above. I don't know how to do anything else or what to do, but if you tell me, I can follow directions.
    Last edited by juddspaintballs; 03-28-2019 at 12:12.

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    You're right about flashing the field, normally you can hold the starter switch after the machine has started and the starter cutout near the oil filter will disconnect power from the starter as soon as the motor starts, but it sounds like that is not working.
    I suppose a quick short cut to test the field flash would be to start the gen. then disconnect the plug going to the starter interuptor ( small oval shaped tin cover to the right of the injection pump and above the oil filter with 1 wing nut holding it on. ) they turn the main switch to start again ( the starter should no engage now ) hold for 10 seconds and see if the gen starts making power.
    If it still doesn't make power you could have a voltage regulator problem or possibly a bad winding in the CVT.
    Try getting the field flashed and let us know if it makes any difference. if it does we can then get your starter interruptor fixed next.

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    As for the voltage and Hz meters, assuming the gages are reading correct, the Hz being pegged means the throttle is set too fast and needs to be backed down to read around 61.5 hz at no load. Sounds like the voltage is set too low as well. 91VAC at plug and 180 on meter because your AM/VM switch is set to read 240V on the gage when operating correctly.
    Try turning the volt adjust knob up. If you can't get it up to 240 on the gage there might be another problem going on, possibly with the voltage regulator.

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    With the motor running and that plug on the starter interrupter unplugged, there is no change to voltage and the starter noise isn't happening anymore.

    The Hz meter being pegged to the left means 55 Hz or less. The throttle is not set too fast if that's the case. I trust my Fluke meter more than that gauge, anyways. Fluke says ~60hz at the plug at the current RPM, which is where it's pretty much always been set since I've owned it.

    Turning the voltage knob makes no change in voltage when holding the start switch.

    I found evidence of mice inside the exhaust side flaps. I blew everything out and then opened panels and followed wires. It doesn't appear they chewed anything and they only made a small nest in there. All of the wiring on my genset is fairly new. Nice, pretty, white wires with plastic coating on them like the unit was refurbished before it was stored.

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    So evidence points towards a bad voltage regulator?


    Power is back on now, but I still need to fix this generator. What are people's thoughts on the Lakeland voltage regulator for about $200?
    https://www.lakeserv.net/mep/ac_regulator/index.html

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    Up above you stated the Hz gage was pegged all the way up above 65Hz, not down at below 55.
    If that's the case your Frequency transducer is probably dead.
    Sounds like first you need to jump out the oil and temp sensors one at a time and determine which is the problem.
    Once you get it to stay running we can work on the power output issue.

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    The frequency pegs at 65 Hz only when I'm holding the start switch while the interrupter is still plugged in (and starter spinning). It drops back to 55 Hz when released.

    The motor stays running just fine.

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    Ray, Judd,

    If you measure 60 hertz at the 120 volt outlet, then the main gen is working. The freq meter uses a frequency transducer. That transducer takes a reading off the T1 and T2 transformers. The freq transducer converts 120 volts AC to a DC current to push the meter. So someplace is 120 volts. It sounds like your getting excitation so long as the S1 is in the start position. Then it drops off when you let S1 go. Its late, I had a long day, but when I look at the schematic, if the S1 excites the main gen, then it sounds like the A4, VR is not taking over. Someone correct me if I am making a mistake.

    Edit: Now, after reading post #7, that confirms the main gen working while S1 is held up.

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    Quote Originally Posted by juddspaintballs View Post
    So evidence points towards a bad voltage regulator?


    Power is back on now, but I still need to fix this generator. What are people's thoughts on the Lakeland voltage regulator for about $200?
    https://www.lakeserv.net/mep/ac_regulator/index.html
    I don't think their is enough evidence to pinpoint the VR as the culprit at this stage just yet. There are multiple transformers not associated with the VR board that influence voltage. There are ways to Ohm out the transformers but I don't recall which manual has the test info off the top of my head.

    However, with that said... should it be determined that it were the VR board causing your problem, the Lakeland VR board developed by SS member "TripleJim" is an excellent upgraded replacement VR. I have one in one of my units and it has performed flawlessly. It will dissipate heat much better and the transistors he uses are much better among other things. Although, its worth noting that the OEM Milspec VR board is repairable in most cases.
    #1 House Gen PU-751/M: 1986 MEP-002a/M116A2 w/Aux Tank & OEM cover
    #2 Spare Gen PU-751/M: 1991 MEP-002a/M116A2 w/Aux Tank & OEM cover
    #3 Shop/Barn Gen NF-2 Enclosure: 19?? MEP-002a w/Aux Tank

    * Disclaimer - My comments on this forum are based on my opinion and my experiences only. Any information or suggestions I share could sometimes be inaccurate or misinterpreted. It is your responsibility to verify any information before using or to hire a professional.

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    The -34 TM has the test procedures. When I get back to the barn, I will look them up.

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