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MEP 804b wont crank

expeditionnw

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THank you for your diagrams, and your help in general!

S14, are you referring to the board with the blue metal shell in this photo? I do have power thru the CR4 diode. however, pin 18 on the blue board has no current in any S1 position, but pin 19 has 22v in start position.




View attachment 823189

Forgive my confusion, I am still learning how this information is laid out. My control panel does not have an S14 (Crank disconnect switch).
 

expeditionnw

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Ive done some more digging tonight, after jumping pins 18-19 on the governor control board (the blue thing) the unit cranked when S1 was turned to start. I believe my issue lies within the governor board.

EDIT: Found a test for the GCU (A5) governor control board. using the attached test sequence, I am confident my GCU has failed.

No voltage measured between 19-20 when SI is in start.
Battery voltage measure between 18-19 when S1 is in start.

1610347151039.png
 
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Guyfang

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My mistake. I thought the S14 was a plastic relay. And it part of the A5. I guess Kurt set you straight. Sorry.


There are 2 part numbers for the A5. Part numbers 97-24134 and 8270-1096. Both show a NSN of 2910-01-571-1364.

The part # 0270-1036 is not to be found in the Fed. Loc System. Did you take it off the A5?
 

Guyfang

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I talked with someone in CECOM. He told me there is another A5 that fits both the A&B models. So universal. NSN 2990-01-601-2476, Part # 88-22850 and part number ESD5560, (Governors America Corporation.) I looked in epay and found under the part #ESD5560 one listing. Be prepared for sticker shock.
 

expeditionnw

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I talked with someone in CECOM. He told me there is another A5 that fits both the A&B models. So universal. NSN 2990-01-601-2476, Part # 88-22850 and part number ESD5560, (Governors America Corporation.) I looked in epay and found under the part #ESD5560 one listing. Be prepared for sticker shock.
I ordered a NOS unit for relatively cheaper just before you posted. It came in today, and looks identical visually. The part number is slightly different. I dont know how the PN codes,out, but hopefully its interchangable because its in now. The replacement came with the pots clocked the same as mine so that promising.

mine:
PN 8270-1096 Rev. NEW

the replacement:
PN 8270-1002 Rev. B

Also received my new MPU. going to install this as well. Have to wait till my batts charge tonight. Some idiot must have left the S1 control on last time they worked on it :)
 

Guyfang

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I ordered a NOS unit for relatively cheaper just before you posted. It came in today, and looks identical visually. The part number is slightly different. I dont know how the PN codes,out, but hopefully its interchangable because its in now. The replacement came with the pots clocked the same as mine so that promising.

mine:
PN 8270-1096 Rev. NEW

the replacement:
PN 8270-1002 Rev. B (This comes up with a NSN of 2910-01-368-7644. It also shows 5 different part numbers. )

Also received my new MPU. going to install this as well. Have to wait till my batts charge tonight. Some idiot must have left the S1 control on last time they worked on it :)
 

expeditionnw

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Interesting that its a different NSN, though they appear to be the same part. I pulled the cover and the board looks identical.

Think its a bad idea to try it?

What could be different? I confirmed the replacement is for a 15k gen set, though not sure which.
 
Last edited:

expeditionnw

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I installed and set the mpu, installed the Gcu.
Looking closer, the pots are set differently on the replacement panel.

(See pic- top is newly installed 804a gcu, lower is original 804b gcu)

I adjusted the newly installed replacement panel to match the original. Didnt touch the freq or overspeed pots because im not sure which way is which.

i have the gcu adjustment table for the 804a, does anyone know if its the same for the B?

anyway, from S1, it started immediately and ran with no issue.
 

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Guyfang

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Someplace towads the begining of this thread, (or maybe another thread?) I posted that someone in the know tolld me there is no difference to speak of, between the A and B model GCU. So if it runs, go for it!
 

Jcounahan

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I'm having this problem and will probably venture out to remove the cover from my governor control board and check for fried components in a few minutes. The only difference is that sometimes my set will crank and either runs too fast (62hz+but has only shut down for overspeed a couple times) or slow (58hz), and the frequency knob doesn't change the engine speed when it does run. As of right now fuel pump comes on and I get a click when I turn s1 to start, fuel pump remains on as long as I hold start but shuts down when I release to run, it hasn't done more that this in the last few attempts to start.

I've done a search and I'm seeing one woodward generator control board for sale except it has the part number:

8270-1003 Rev. B

The one you guys referenced here shows 8270-1002 rev. B

Can anyone tell me if they interchange? Maybe the 1003 part number is for the mep-804B model instead of the A model? I know that's a best case scenario, but these parts are turning out to be hard to find.
 
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