MEP-805A 24 volt problem

[Flowmastr]

Hello everyone, I have been searching for answers but not getting far. A friend has a 1993 MEP-805A with 21 hours on it. To begin with was it would sometimes/run start but when it it would not crank he showed me how he drops the control panel down and wiggles the wires in the area of S1 and S17 and it would turn over start and run. So now it was going to be stored at my shop and before transport, he tried to start it, no go even with the wire wiggle. I found the wire on #8 of S1 off. No big deal I thought. Now it is at my shop and I attached the wire back on terminal #8.
Issue: No crank, no control panel power. 24 volts on both sides of S17 pulled out with S1 off. 24 volts to DC control panel breaker and 24 volts to #3 on S1. When you turn S1 to prime/run or start, all 24 volts go away. Nothing on S17, Control panel or S1. Any insight would be greatly appreciated

 

[kloppk]

Does the set Dead Crank reliably?

The -24 TM has the schematics for troubleshooting. It also has a section for no crank troubleshooting.

Watch the DC voltage at both ends of CR1 to see it both stay around 24 volts when attempting to start. They should.
Check the DC voltage on any terminal of MT4 to see if it stays around 24 volts when attempting to start.

Post up what you find.

 

[Flowmastr]

Yes it dead cranks. will look into the rest today, thank you

 

[Flowmastr]

This one ? TM 9-2815-255-24P

 

[Flowmastr]

Batteries charged
Dead crank-Yes
S17- pulled out 24.5 volts both sides
S1- off 24.5 volts pin 3
CB1- 24.5 volts both sides
CR1- 24.5 volts both sides
S1- master switch- any position but off, No 24 volts on any of the previous listed places

As previously stated it would crank and run with a jiggle of the control panel harness around the stop/master.

 

[kloppk]

This one ? TM 9-2815-255-24P

The TM to look at is: TM 9-6115-644-24
** Corrected TM #

 

[kloppk]

If you're losing power to CR1 then it looks like there is a continuity issue from the dead crank switch S10 terminal 3 to CR1 terminal 1.

Here is the wiring path from S10-3 to CR1.

------------ wire# 178A --------------------wire# 178B----------------wire# 178C
S10-3----------------------P6-8-- J6-8----------------------TB4-6------------------------------CR1-1

S10's rarely go bad.
Need to check along the path above to see where the 24 volts is getting lost.
My first hunch is that the connection between P6-8 and J6-8 is making poor contact due to corrosion.

 

[Flowmastr]

24 volts all the way thru to CR1 from S10. As soon as the e stop is pulled out, I lose 24 volts on the left side of CR1

 

[Flowmastr]

E-stop out- 24volts both sides
Master off- 24volts Pin 3
CB1- 24 volts both sides
CR1- 24 volts both sides

Estop out
Master switch prime/run
CR1- 178C 24volts, 162A .0132 volts
Everything else previously with 24 volts- .0132 volts

Estop out master off, panel light has 24 volts in the off position drop to .0132 in the on position

 

[kloppk]

Sounds like a bad CR1.
It's a 1N5406 3 amp diode.

 

[Flowmastr]

Is this common or how it behaves when bad?

 

[kloppk]

Moderately common failure of CR1.
The voltage on both sides of CR1 should always be about 24 Vdc with Dead Crank in Normal and regardless of the position of S1 or S2.

 

[Guyfang]

This one ? TM 9-2815-255-24P

No. This is an engine TM.

 

[Flowmastr]

So, new 1N5406 3 amp diode. Fired right up dragged it outside ran it a bit. Shut it down, no 24 volts. Well wiggled the connect p8-J6 connector'
Yup, 1 corroded pin set. cleaned up all good, thank you Kloppk.
One more question, upon start up the under current light will come on, I dont think all the the time, but after resetting lights goes out and able to close ac interrupter and produce power. Also have to tap on AC gauge once in a while to get accurate voltage on the dial