MEP-003a No voltage

[juddspaintballs]

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.

 

[Ray70]

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.

 

[Ray70]

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.

 

[juddspaintballs]

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.

 

[juddspaintballs]

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

 

[Ray70]

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.

 

[juddspaintballs]

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.

 

[Guyfang]

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.

 

[Chainbreaker]

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.

 

[Guyfang]

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

 

[jamawieb]

4 items I would check.
CVT1 transformer. Big black transformer on the bottom of the output box. Its actually 2 transformers mounted together CVT1 is in the back
Exciter board A4
VR. Sometimes to check the VR you can take number 17 off the VR board and tape it up. Start the unit and if voltage is present (usually will produce 300+volts), the VR is bad.
Linear reactor which is mounted on the left behind CVTI

 

[Guyfang]

Do you need someone to look the test procedures up? I am home now, and will be near this computer for 4-5 hours more, till bed time.

 

[juddspaintballs]

Sorry, I've been at work since about 0100 Friday morning. I'll be home around 0800 Sunday, but I won't be around most of the day and I work again on Monday. At the earliest, I won't be able to touch the generator again until Tuesday. If I get the chance at work tonight, I'll see about downloading some manuals.

I was reading through this thread:
https://www.steelsoldiers.com/showt...e-or-HZ-reading-on-meters&highlight=glow+plug

It got me thinking. If the sensor didn't pick up that oil pressure had risen, then it wouldn't signal the VR to take over, right (post #33). It also wouldn't signal the starter interruptor. So when I turn the master switch to start for flashing, the starter tries to engage and the voltage rises, but not high enough because maybe some of the battery power for flashing is being redirected to spin the starter at the same time or the starter trying to spin could be slowing the motor down maybe (just spit balling). So basically, if the oil pressure sensor isn't working, when I flash the field the starter tries to spin still and when I release the start switch that the VR doesn't take over. Does any of that make sense?

 

[Guyfang]

The oil pressure switch, S5, has absolutely nothing to do with your volt Regulator, (A2). Please look at the schematic. On start up, the whole engine safety chain, S5 and S4, (engine temperature) are bypassed. Look at S1 schedule. On start up, pins 11 & 13 & 15 & 25 & 27 and 28 are hot. Why? Well, S4 is a normally open switch. Until it can come up to pressure, you have to bypass it. hence, pin 28 on S1. It allows you to power up the gen set, and let the engine run. Then when you let go of S1, and the S5 has closed, the gen set can continue to run, because pin 14/14 are now providing voltage to the K5, (engine solenoid).

Pin 27 is the initial excitation. When the A2 senses voltage from the initial excitation, then you let go S1, the A2 takes over providing excitation. But the S5 has nothing to do with that. Your starter grinds when you try and hold the S1 up because the S7 is maladjusted, broken or the wires are broken. And that the only reason it grinds. So you need to check the wires, canon plug and then read the procedure to test/adjust the S7. That's something you can easily do.

 

[juddspaintballs]

I am at work again today, so I'll be home Wednesday morning and finally able to look at this thing again. I downloaded the -12 and -34 manuals. Anything in particular I should start with diagnosing?

 

[Guyfang]

As a warm up, fix the S7. Then you can hit the S1 to excite or re-excite the main gen. Then try and start it again, like normal. Then go back to post #11 from jamaweib. Test the VR.

 

[juddspaintballs]

I'm having a heck of a time figuring out where everything is in the manuals. It's a whole different language to me at times. I only found mention of S7 one time in the -12 and -34 manuals and that was just mentioning that it would disengage the starter when the switch was turned to start while the motor was running.


So the S7 is the thing that disconnects power to the starter? The thing over by the injection pump above the oil filter canister. This:





The copper flat is supposed to be pushed up away from making contact by the red rubber plunger. That doesn't happen while the motor is running. I took it off and was able to push the plunger by my finger and it worked fine. If I manually move the copper flat away from making contact while the machine is running then try the start switch, the start doesn't engage (as it isn't supposed to) but my gauges are all to their most left extreme - no reading. So even after I fix this S7 issue, engaging the start switch (is that S1?) still doesn't flash the field and get me to where I need to be.




Also, my batteries aren't charging. Never have since I owned it. The fuse for the DC system is good. DC voltage from the stator is 14.38 on one lead and 14.37 on the other with 24.48 coming out of the regulator. I realize that this is an entirely different issue, but I should probably address it the same time.

 

[juddspaintballs]

I found out how to adjust the starter interrupt switch in the -12 manual. I'll work on that tomorrow.


What's next once I get that adjusted to work properly? With the set running and that switch unplugged, the field doesn't excite and hold voltage.

 

[juddspaintballs]

Starter interrupter switch is now working properly. When engine speed comes up, the push rod moves the interrupter switch so the starter doesn't engage while holding the start switch. No voltage at the output lugs, no voltage or frequency on the gauges, no voltage at the convenience outlet.



Is my next test to follow procedure 8-2 in the -34 manual? "Disconnect the voltage regulator at the exciter wires (wires P67C16 at TB3-5 and P60E16 at TB3-6). Connect a 12 volt battery in place of the regulator with the (+) terminal to TB3-6 and (-) terminal to TB3-5. Run the engine with the battery in place of the voltage regulator. If there is output now, the voltage regulator is bad. If there is no output, the main alternator is bad."

 

[Guyfang]

Start the gen set up. While you do that, have someone use a multi meter to check the input side of the frequency transducer, for 120 VAC. At the beginning of you thread, you spoke of a reading on your hertz meter. If the hertz meter gives you a reading, it's getting 120 VAC. So let's confirm what's happening here. There is a world of difference between no AV output and not getting output on the load terminals.