MEP-002a keeps kicking off line

[twitchit]

RESOLVED!


Hey guys, Im new on the board and just picked up my first military gen, an mep-002a. I changed the filters, oil, and drained and refilled the fuel. Got the engine running but I cant seem to get the gen set to keep power going out. holding the switch to start seems to make it work as long as I dont let go, but the meter reads pegged out Htz. I tried looking in the TSM but cant seem to find my problem in the TS section. I dont know where else to turn. I dont even know where to start troubleshooting. Any help would be appriciated.

OK I figured out i can get the HTZ down to 60 at about half throttle. I still have the problem of not putting out power without holding the start switch. When i hold it in start position, it does put out voltage to the proper lugs. when i let go the power drops off. The main circut breaker works fine and it doesnt trip.

 

[Speddmon]

Bad voltage regulator

 

[twitchit]

Has anyone had luck replacing parts on there voltage regulator? I see a burned diode on it. I wonder if I can just replace the diode.

 

[LuckyDog]

Spend some time searching this forum. It has been covered a lot. It is easier and cheaper to fix than to replace.

Links might not work, or might now. We just went through a major site upgrade. Things are still being worked out.

and PLEASE, read the manuals, and DON'T ever idle the machine.

Search and the WIKI are your friends.

 

[twitchit]

OK Im still stumped. I changed the voltage regulator with one from a 003a. It still doesn't work. I can get voltage at the post only when I flash the fields. Also I noticed I don't have voltage at the battery gauge. I Thought it was the gauge at first but I got nothing in the wire. Any thoughts?

 

[LuckyDog]

Ok, one problem at a time. I'm ignoring the battery meter for the time being.

I attached a section of the schematic from the manual. (You DO have a copy of the manual, right? )


Make sure the wires I have marked with green arrows are there and the connections are good.

Make sure T1 and T2 are there, connected properly, and the good connections. With out the transformers(and wires) the VR won't power up.

Just guessing. I've assumed the VR you tried was known good? i.e. working in the 003 before you put it in the 002?

Good luck.

(Thank God for the Edit button's return)

 

[twitchit]

I traced all the circuits from the xformers to the diodes on the vr. I even checked the diodes on the vr. all of the connections were good and all the wires ohmed out. Then I checked the t1 and t2. t1 was spot on. t2 was supposed to be 155 ohms +- 1.55 between h1 and h2. I got 138 ohms there. x1 and x2 checked out good. Does this mean t2 is bad? and if so would it probably be the cause of my woes or is it just a part that is marginally working and shouldn't cause the problem unless it was fried completely?

I know they put limits there for a reason. I am a licensed A&P and build jet engines. We use limits to determine the serviceability of a part. We would never build an engine using parts that unserviceable due to out of limits. With that being said, one could build an engine with out of limit parts and it may effect the performance of it, but may not keep it from meeting a certain level of performance.

What I am trying to say is will that much difference in resistance would it cause my genny to not connect? I will try to swap t2 out with the one in my 003a tomorrow.

 

[LuckyDog]

Don't know if the lower resistance on T2 would do it. opcorn: Let us know.

There are two jacks / connections in the schematic that should be checked while you are in there. J2 and J11. If there is a bad connection there, that would prevent current flow from the VR to the exciter field. J2 is on the "Control cubicle assembly" J11 is on the "Control box assembly". (I did not make these names, geez)

And if you can, check out the resistor and diodes on A4 (Bridge rectifier assembly). That one is inside the Control box assembly.

 

[twitchit]

Im still beating my head against the wall. I see the exciter field. What voltage dose it use?

I checked all my wires and they rang out good. I changes the T2 and still no dice. Why does the exciter field only work when I flash it with the switch? I hope I don't have 2 bad voltage regulators.If it is indeed the voltage regulator, does anyone know how to definitively check them? Is there anyone who rebuilds them?

 

[LuckyDog]

Im still beating my head against the wall. I see the exciter field. What voltage dose it use?

http://test.steelsoldiers.com/upload/Generators/TM5-6115-585-34.pdf This TM has a procedure to test and adjust the VR

I checked all my wires and they rang out good. I changes the T2 and still no dice. Why does the exciter field only work when I flash it with the switch? I hope I don't have 2 bad voltage regulators.If it is indeed the voltage regulator, does anyone know how to definitively check them? Is there anyone who rebuilds them?

Did you check your Bridge Rectifier Assembly A-4 Diodes? See manual linked above.

 

[twitchit]

Wow! That did it!!!!! CR5 on the bridge board! Everything looked fine on it so I pulled it out and checked it anyway. With your help I found it. Thank you so much! now I get to clean her up and play with her. I am stoked and I learned a bunch about these things.

 

[twitchit]

Now I get to troubleshoot the battery gauge. Not getting power at A1-4 with the switch on. Should be an easy one to fix. maybe its the relay itself. I got power to A1-3.

 

[LuckyDog]

K-1 won't stay energized unless the motor is running.

You can fool it though. Take the leads off the oil pressure switch, short them together. Then turn the start switch to the start position and release.

K-1 will have energized. The engine thinks it has oil pressure and is not over temperatured. Now check A1-4. Trace wires, check connections, etc.....

Don't forget to reconnect the oil pressure switch back. It is you insurance against running without oil pressure.

 

[twitchit]

Very good to know. I was checking for voltage without it running. No wonder. I figured it was like an ignition switch on a car. Thanks. It probably works 4.0 and it was just my ignorance and assumptions.