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MEP-802A Relay Pinout?

Jerds19

Member
30
22
8
Location
Austin/Texas
Hello all, having a starting issue and I can't figure out why my Cranking Relay (K2) isn't getting any power when trying to operate from the front panel switch (S1).
X2 has ground no matter what position S1 is in.
X1, A1 and A2 never receiver power, regardless of S1 position (prime/run or start).
Fuel solenoid (L5) never receives power or actuates regardless of S1 position.
When setting S1 to prime/run the fuel pump actuates and gauges work, relays inside actuate assumingly correctly as some of them tick.
When setting S1 to start, there is an audible clunk coming from the starting solenoid (L4), and voltage drops from 24ish down to 20ish, but there is no cranking attempted.

When use the dead crank switch (S10) the cranking relay does get power to X1, A1 and A2, the generator will crank but will not start because fuel solenoid never receives power/actuates. If I manually retract fuel solenoid and crank from S10 it will start and run, produce AC power and work fine until I release start solenoid and then it shuts off.

So I know the batteries, starter, starter solenoid work.

I have gone through the -20 per advice from users on this forum and everything tests out fine up until step 18, "test for defective cranking relay". The tests don't however tell you WHICH wires are suppose to be powered coming into the K2, but since NONE of them are getting power there is obviously an issue. (Going past 18 to 19 and 20, I have confirmed 19 start solenoid works, and 20 starting motor works).
Assuming the device prior to the cranking relay in the electrical circuit would be one or two of the relays... S14? K12? K16? maybe all of them working in unison?

One of my concerns is that on S14, there are no wires connected to the A or B (activation) terminals, so there is no way to actually actuate the relay. This might be normal as they do call this a "switch" not a "relay". But it is entirely possible that there are missing wires on this unit, which will likely make it a nightmare.

Can anyone help me understand which pins are suppose to be powered on these relays when the generator is in the "run" position? I'm looking at the F0-1 Schematic, and I see the flow charts, but can't find anything that shows pinouts. All the troubleshooting tells me is how to confirm the relay is WORKING, and all the relays appear to be perfectly functional, but that doesn't confirm that all the wires into the relay sockets are wired properly (or there). It appears to me that for some reason, there is probably one wire that suppose to be hot that powers the start relay and the fuel solenoid that isn't going hot, and I can't figure out why.

There are no diagnostic lights showing errors, and again it will start and run from dead crank switch with fuel solenoid held open, so that tells me that there is enough things connected properly for it to crank and run from dead crank, just not from S1. So I feel like there is some "check" or "sensor" that is telling the system it isn't ready to run, but I can't figure out what. I have been told, which may be incorrect, that if the unit is low on oil or fuel the unit won't crank and run. However the "engine fails to crank" flowchart on page 54 never even mentions those things.

Any advice would be appreciated!
 
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kloppk

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Here is the pinout of one of the KUP relays in the row. It depicts the screw terminals on the sockets. The terminal numbers are also molded into the sockets.Screenshot_20220809-185051_Adobe Acrobat.jpg

I believe you meant S14 not S12. There shouldn't be any wires on the A and B terminals. S14 isn't a relay. It's a Frequency Trip switch that is used for starter cutout and Field flashing.

The -24 TM has the schematics as well as the exact wiring. The schematic shows how things are electrically connected but not how they are physically interconnected. The component diagrams after the schematic shows how things are physically interconnected.
 
Last edited:

Jerds19

Member
30
22
8
Location
Austin/Texas
Here is the pinout of one of the KUP relays in the row. It depicts the screw terminals on the sockets. The terminal numbers are also molded into the sockets.View attachment 875379

I believe you meant S14 not S12. There shouldn't be any wires on the A and B terminals. S14 isn't a relay. It's a Frequency Trip switch that is used for starter cutout and Field flashing.

The -24 TM has the schematics as well as the exact wiring. The schematic shows how things are electrically connected but not how they are physically interconnected. The component diagrams after the schematic shows how things are physically interconnected.
KloppK, thank you for the reply and time!
You are 100% correct I MEANT s14 when I wrote s12, I just updated the original thread.
Can you expand a little bit on the S14 being a frequency trip switch? In my unit the S14 is a clear housing device, that looks identical to the 5 relays (not clear housing) directly to the right of it. It also tests out to work just like the relays (open/closed connections, activated by A and B). Maybe someone put a RELAY in there and it's suppose to be a completely different device, and that might be the (or a) problem?

Also, can you tell me where these component diagram are located, maybe a page number? I tried looking in the table of contents and don't see where they'd be, also tried searching "component" and found nothing. I clearly am under qualified to be using a -20 manual! All I'm finding are the wiring schematics, but the one you just listed should give me at least a little more info!
Thanks again!
 

kloppk

Well-known member
Steel Soldiers Supporter
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Pepperell, Massachusetts
The leftmost item in the row is S14. It should NOT be a relay. S14 is in a relay case but contains a circuit board with an IC and a few other components on the circuit board inside it.
If you have a regular relay in that location then that is likely the problem.
I have S14's available in the forums Classifieds should you need one.
 

Jerds19

Member
30
22
8
Location
Austin/Texas
The leftmost item in the row is S14. It should NOT be a relay. S14 is in a relay case but contains a circuit board with an IC and a few other components on the circuit board inside it.
If you have a regular relay in that location then that is likely the problem.
I have S14's available in the forums Classifieds should you need one.
Hey dude, I THINK this is a problem... On mine the left most (S14) is a different housing, but it has all the pins on the bottom of it just like a relay, and tested out just like a relay. So I THINK someone just put a different looking relay in there! Here is a picture I took earlier, not high enough quality to zoom in and get better information/part numbers to verify what it really is. But I'm gonna check that first thing tomorrow morning!!!! Thank you!
Or maybe you can tell from this picture if that is, or is not the frequency trip module?
 

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Jerds19

Member
30
22
8
Location
Austin/Texas
Hey all, Thanks to the help of Kloppk and Light in the Dark the problem was identified, Kloppk is sending me a new frequency switch, and he even told me how to temporarily bypass frequency switch function to get it running and we confirmed everything else on the generator starts and runs as it should once that frequency switch arrives and gets installed!

It is an awesome feeling when you can get something that "does not run" to "run" and bring it back to useable service.

Big thanks to these guys for taking the time to find and help me solve the problem!

I hope one day I'll have learned enough to share my experiences and do the same for another.
 
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