mep 803a stopped on its own, wont turn over via main switch, has battery power

[Zed254]

Good info here on failed alternator diodes: https://www.steelsoldiers.com/showthread.php?143877-MEP-802a-Low-Alternator-Voltage-Output

May help with your rebuild. MEP802A and 803A use the same alternator.

 

[Ray70]

Gunny, Guy is right, I'd get your batteries charged up and test your alternator. If you aren't getting close to 28V out of it, it is bad. You can get a replacement for $180 but you also might only need a new regulator. I've occasionally seen them for $40, but few and far between.
The TM tells you how to test the windings in the alternator, but you will probably find that your alternator does not look like what the TM shows. The TM makes it look like the rectifier and diode trio unbolt, but they are soldered to the windings.
You can still test the resistance of the stator windings and if they are good, just see if you can locate a new regulator, fix the old alternator and keep it for a spare.
I just fixed one of mine this week, was able to combine 2 bad alternators into 1 good one ( and one really bad one now ) by swapping the regulator off one with a bad diode trio onto one with a bad regulator ( that had no output ).

 

[Guyfang]

Gunny, Guy is right, I'd get your batteries charged up and test your alternator. If you aren't getting close to 28V out of it, it is bad. You can get a replacement for $180 but you also might only need a new regulator. I've occasionally seen them for $40, but few and far between.
The TM tells you how to test the windings in the alternator, but you will probably find that your alternator does not look like what the TM shows. The TM makes it look like the rectifier and diode trio unbolt, but they are soldered to the windings.
You can still test the resistance of the stator windings and if they are good, just see if you can locate a new regulator, fix the old alternator and keep it for a spare.
I just fixed one of mine this week, was able to combine 2 bad alternators into 1 good one ( and one really bad one now ) by swapping the regulator off one with a bad diode trio onto one with a bad regulator ( that had no output ).

Hey Ray!

Good info. One of the reasons the alternator doesn't look the same as the book is because there is and old and new version of the alternator. But its not hard to test or check. And not all that hard to fix. Read the TM, and if that's not clear enough, someone like Ray can give you a pointer or two. If you have to buy a new one, what you got to loose? Might even be something like a loose connection. But first charge the battery's up, tip top. Then test.

 

[Gunny65]

I tested the alternator. No go. It is dead. I ordered a new one. $127 including shipping, from the UK. The only thing it needs is the pulley and a capacitor. It is an exact match. I'll let you know how it goes when I get a chance to install and test it. Thank you for the help.

I also learned a lesson. If your appliance has a clock, or continuous memory of some sort, with no surge protector, it may be destroyed if your alternator goes out and you don't notice until the genset goes off on its own. I lost an Air-conditioner, a microwave and a underground dog fence controller. That turned out to be an expensive lesson. Surge protectors FTW.

 

[Gunny65]

I am not finding a cross reference for the capacitor that is on the alternator. Leese Neville shows capacitor part number as: 0844474C02S

I called auto zone and napa and they do not show anything on the part number or name. Has anyone needed to purchase a replacement capacitor and/or do you have a viable part number that I can use for local auto stores?

I could order one online using the part number I have but it would take a few days. Would like to fix this sooner than that.

 

[Guyfang]

The alternator you ordered is not a standard alternator that the military uses. I have never seen one with a cap, mounted on the back side. I am going to believe you when you tell me its the right one, but where did you get this info?

 

[Gunny65]

The alternator you ordered is not a standard alternator that the military uses. I have never seen one with a cap, mounted on the back side. I am going to believe you when you tell me its the right one, but where did you get this info?

That may be Guyfang. I simply used the alternator information that is/was installed in the generator to order the new one. The original alternator has the green over-spray paint they used on the tier two reset they did back in 2010. The regulator on the back has the same model and nomenclature as well. It may not be the original but it is what they put back on at Letterkenny army depot. I assume by "the cap" you mean the black regulator?

Zed254 found the alternator I ended up ordering. Ended up being about $50 cheaper than any others I could find.

Do you happen to know which capacitor I need to order?

 

[Zed254]

The end of the alternator needs to be turned around, too. The way it comes from factory (at least my spare) does not match the configuration as mounted on the 803. Directions about this alteration is on another thread that I haven't been able to find.

This is what I have for alternator: PRESTOLITE LEECE NEVILLE 8MR3005C CAR 8RG3063 GENERATOR ALTERNATOR TRUCK 24V , NSN IS 6115-01-368-2911

 

[Guyfang]

The cap I wrote about is the Capacitor. If you look at the -24P, exploded picture of both types of alternators, there is no Capacitor on them.

Part number 8MR3005CA, NSN 6115-01-459-1661
Part number 8EM3005CA, NSN 6115-01-459-1661
Part number 88-21154, NSN 6115-01-368-2911
Part number 110-489, NSN 6115-01-368-2911

The top two numbers are the newest, with the top number being the absolute newest. Same NSN, but different PART NUMBER.

 

[Guyfang]

The end of the alternator needs to be turned around, too. The way it comes from factory (at least my spare) does not match the configuration as mounted on the 803. Directions about this alteration is on another thread that I haven't been able to find.

Simply take out the 3 long screws, rotate the head, and install screws. They all can come like this.

This is what I have for alternator: PRESTOLITE LEECE NEVILLE 8MR3005C CAR 8RG3063 GENERATOR ALTERNATOR TRUCK 24V , NSN IS 6115-01-368-2911

.

 

[Zed254]

Green Mountain says the only difference is the end of the alternator needs to be rotated.

"Direct current generator/alternator for MEP802A, MEP803A, MEP812A, MEP813A military diesel generators. NSN: 6115-01-368-2911 (found in the MEP802A and MEP803A parts manuals), 6115-01-459-1661 (NOT found in the manuals, but crosses with DOD # 88-21154, which IS in the manuals). Both of these are identical alternators with the only difference between the 8MR3005C & the 8MR3005CA is that the rear housing of the 8MR3005CA is rotated 90 degrees counter-clockwise. Both models are used on the MEP802A and MEP803A units. This unit comes with 8RG3063, the voltage regulator"

https://greenmountaingenerators.com...alternator-6115-01-368-2911-8mr3005c-110-489/

Sure hope so because the 8MR3005C is the one I had to rotate the head on and is now located on my spare parts shelf.

 

[Gunny65]

The cap I wrote about is the Capacitor. If you look at the -24P, exploded picture of both types of alternators, there is no Capacitor on them.

Part number 8MR3005CA, NSN 6115-01-459-1661
Part number 8EM3005CA, NSN 6115-01-459-1661
Part number 88-21154, NSN 6115-01-368-2911
Part number 110-489, NSN 6115-01-368-2911

The top two numbers are the newest, with the top number being the absolute newest. Same NSN, but different PART NUMBER.

Yes, the top part number is the alternator I ordered and received. It did not come with the capacitor which was the reason I was asking. I did not see it in the 24P either. Sooooo, I guess that means we don't know why Letterkenny put one on the original (to me) alternator.

It seems the capacitor is used to even out alternator noise fluctuations. The only guess I have is to help ensure the power to the generator is clean?-Wild guess. I know they are normally used for reducing audio alternator whine in a car but...here I don't know. Was hoping somebody here knew.

I guess my final question to the people who know, Should I get new one or ignore it since it isn't included in the 24P exploded view?

 

[Gunny65]

Green Mountain says the only difference is the end of the alternator needs to be rotated.

"Direct current generator/alternator for MEP802A, MEP803A, MEP812A, MEP813A military diesel generators. NSN: 6115-01-368-2911 (found in the MEP802A and MEP803A parts manuals), 6115-01-459-1661 (NOT found in the manuals, but crosses with DOD # 88-21154, which IS in the manuals). Both of these are identical alternators with the only difference between the 8MR3005C & the 8MR3005CA is that the rear housing of the 8MR3005CA is rotated 90 degrees counter-clockwise. Both models are used on the MEP802A and MEP803A units. This unit comes with 8RG3063, the voltage regulator"

https://greenmountaingenerators.com...alternator-6115-01-368-2911-8mr3005c-110-489/

Sure hope so because the 8MR3005C is the one I had to rotate the head on and is now located on my spare parts shelf.

I will need to rotate the rear. It will fit as is but the regulator is upside down.

 

[Zed254]

Yes, the top part number is the alternator I ordered and received.

Excellent!!! My pucker factor was getting pretty high. Was afraid I had pointed you in the wrong direction.

When I was checking my 803 (It's alternator looks like a rebuild - no black paint) I remember seeing that capacitor. It is a 2011 reset.

I just checked my 802: It has a freshly painted 8MR3005CA alternator but no capacitor. It is a 2008 rebuild.

So not sure about your capacitor. I usually reinstall what was in place but as you noted, the capacitor is not in the TM. Maybe Guyfang will chime in ....

 

[Gunny65]

Hmmm, so maybe they started putting the capacitors in around 2010? The -24P I have is October 1996 version. It is the one I got off this site so I imagine everyone is using the same older TM. I wonder if there is a newer one that was made or had a posted change done around 2010. I'll have to look around.

Edit: I found 1992 and 1996 versions. Nothing newer. Does anybody have any contacts, military wise, where we could get a newer version, with changes?

 

[Guyfang]

Hmmm, so maybe they started putting the capacitors in around 2010? The -24P I have is October 1996 version. It is the one I got off this site so I imagine everyone is using the same older TM. I wonder if there is a newer one that was made or had a posted change done around 2010. I'll have to look around.

Edit: I found 1992 and 1996 versions. Nothing newer. Does anybody have any contacts, military wise, where we could get a newer version, with changes?

I do have contacts, and looked at a TM that is newer. BUT, its coded not for release to the public. Put the alt. on as is and start it.

 

[Gunny65]

I do have contacts, and looked at a TM that is newer. BUT, its coded not for release to the public. Put the alt. on as is and start it.

I am going to assume since you looked at the TM, and didn't mention seeing a capacitor, it doesn't show one?

I rotated the new alternator housing 180 degrees as suggested, installed it as is (no capacitor), and it is charging the batteries and putting out 28volts. I don't think the old alternator was ever working correctly. It was working the one time I checked after I purchased it but it still had to have been bad for awhile. Meaning it was working intermittently and I don't know when it went totally bad. Anyway, got a new one and the whole panel shows all gauges normal. The charging gauge is a little high of course but it is working as expected.

I hate leaving things unanswered but as to why the old alternator had a capacitor on it? I don't know. Sorry to the next guy who comes looking for that answer.

Cheers!! And many thanks to you all for your assistance.

 

[mciikurzroot]

Where or did I miss that while not shown the 'capacitor' was determined to be BAD.. If not proven bad, then put it on with what you are using if you are just determined to have it on. your assumptions are generally correct about smoothing or filtering the voltage and or noise levels. While the alternator is just that an alternator making 3 phase electricity and then rectified to DC is the regulator's job as well controlling the voltage. But I got confused on your wanting to try and protect interior loads and will share that this capacitor will not offer any protection for any of AC voltage outputs your set produces. Even the varistors in your output terminal board/s are for interior protection of the sets produced voltages, nothing external.
best: mac/mc

 

[Guyfang]

Mac, You are completely right. The installed alternator has an internal RFI Cap in it. As soon as I saw the part number, it was clear to me, just put it on. That was an easy fix. Glad it worked out.

 

[Gunny65]

Where or did I miss that while not shown the 'capacitor' was determined to be BAD.. If not proven bad, then put it on with what you are using if you are just determined to have it on. your assumptions are generally correct about smoothing or filtering the voltage and or noise levels. While the alternator is just that an alternator making 3 phase electricity and then rectified to DC is the regulator's job as well controlling the voltage. But I got confused on your wanting to try and protect interior loads and will share that this capacitor will not offer any protection for any of AC voltage outputs your set produces. Even the varistors in your output terminal board/s are for interior protection of the sets produced voltages, nothing external.
best: mac/mc

Not showing the capacitor in the schematics is not necessarily Bad but it is an unknown and unknowns make it more difficult to troubleshoot an issue I (for those of us who do not normally work on these or similar items). It seems to have been installed during a reset at Letterkenny so they put it on for some reason. I like to know why I add or remove an item from a piece of equipment. I am not an electrician or mechanic so making a determination on what should be left on or off is for the books or someone who is trained in the piece of equipment. While we have an idea of why it was added to the alternator, there is nothing explaining it in the TM. That is my concern, the how and the why are not resolved. It doesn't seem to be a big deal but it is something I think people would like to know. Me being one of them. So, you didn't miss anything. It isn't Bad, just not resolved. I did put it on and run it and it seems to be working fine but there will always be that little nagging feeling asking, why.