Mep-831a won’t crank

[Lettja]

So this set was fine when I went on leave and the people preparing for a mission tried to test if it sent power and it did and they said when they turned it off it would turn back on

I tried troubleshooting from the TM by testing the battery from tp30 to tp31 and it doesn’t even get a volt of 20 to 32 VDC so I swapped the battery with a brand new one and it’s the same issue

I tried to figure out the schematics and it makes me think it’s the starter but it’s been over 4 years since I learned to read them and am not sure

 

[Subjock]

Hello,
It's been a few months, so you probably have figured it out by now. JIC, take a look in the TM section for : Mep831 training.pdf (has the starting ckt highlighted) and the ARMY TM 9-6115-639-13&P (readable schematic)
There is another thread in here that gives all the points to trace the 25v from the battery, through the control panel and to the starter. Be patient, you could have a bad connection anywhere in the path, but you can find the trouble if you go step by step.

Good luck!

 

[LuckeyD]

Good day: Attached is a color coded schematic. Try these steps...(what does the SGT say; supervisor; LAR) I am a retired P&E LAR Mater Tech or STR
1. all off and open, disconnect battery negative then positive, and with a DMM, (Multimeter) measure B+ to B- resistance. Something GOOD, almost 0 ohms you got a dead short and batteries spark when you connect them. If good proceed.
2. close CB1, pull out the E stop S19 and everything in the attached RED should have B+ power to chassis ground or the B-. Recommend checking if B+ is on K2 terminal A1 and the S1 start switch terminal 5. (forgot that estop?; you may train that operator stopping it using the estop with a 19mm wrench) No power measured anywhere, bad- check that connector bottom right area of control box, wiring, A9 battery charger at the red wire. Open manual and use wiring diagram no power thru S19 E stop and it is pilled out, bad S19. Read power at the K2 and S1 good, go on
3. Place the s1 in the run position: Everything in blue in the attached should have B+ power. Hear and watch the hour meter as it should be working. Fuel gage should work, the actuator lifts off stop position with power at PIN F of governor control. This is Good. Bad will be it don't do anything, hit reset switch, ensure S7 battle short is off, and check power from S1 term 4 to S1 term 1 and thru CR2. If all good now move s1 to start
4. S1 in start: everything in green should get B+. Starter engages it attempts to start. Give this a go and see what happens.

 

[Subjock]

Wow, thank you for the clear and detailed procedure and ckt diagram!