MEP 831A Issues with not charging the lugs

[bcheval]

I am having a problem with my MEP-831A. The engine is running well. However, it will only charge the lugs in when I activate (Battle Short) and then close the interrupter. If I start the unit and try to set the interrupter without the Battle short on, the lugs will not charge. Yes, I have the manual and have followed the instructions up to consult the unit level.
Any ideas?

 

[kloppk]

Have you done a Lamp Test of the Fault Monitor to verify all the lamps work?
Are there any lamps illuminated on the Fault Monitor after you start it?

 

[bcheval]

Have you done a Lamp Test of the Fault Monitor to verify all the lamps work?
Are there any lamps illuminated on the Fault Monitor after you start it?

Yes sir, all the lamps are working and no errors. one point though, when I select Battle Short. The engine does not rev up. I assumed it was because it’s not on load

 

[kloppk]

Has the contactor worked correctly in the past for you?

The engine RPM won't change until there is a load applied.
Without a load it's supposed to run at 3,050 RPM.
At full load the RPM would be 3,450 RPM.

I'd suggest making the following DC voltage measurements to narrow down the problem.
1) Connect your handheld meters negative lead to chassis ground.
2) With Battle Short OFF start the generator.
3) Verify that inside the three relays that only the rightmost one has its internal LED illuminated. Is it?

While holding the Contactor switch UP measure the DC voltage at the following points in the following order.
a) S5-5
b) S7-8
c) S7-9
d) K15-8
e) K15-12
f) K12-4
g) K12-12

Post the DC voltages at each of them. They will be either about 0 volts or about 24 volts.
Also answer to question 3.

Here are the terminal layout for the relay sockets. Same layout for K12.

-

 

[DieselAddict]

I hate to overlook the obvious but when the unit starts you are showing AC voltage on the meter and do you have voltage at the convenience outlet?

 

[Dewie38]

If the contactor only closes with batleshort switch on the it's probably the K8 in the inverter

 

[kloppk]

Do the K8 SSR's go bad occasionally?

 

[Dewie38]

I have seen it
If you look at the schematic you can bypass the overload contacts that open the contactor with the battleshort switch.
It just reroutes the ground path to the contactor.

 

[kloppk]

Should one attempt to replace the K8 SSR to retain the the OL function?

 

[Dewie38]

If one can
In production we would reject the inverter and send it back for repair install another and keep going

 

[bcheval]

Has the contactor worked correctly in the past for you?

The engine RPM won't change until there is a load applied.
Without a load it's supposed to run at 3,050 RPM.
At full load the RPM would be 3,450 RPM.

I'd suggest making the following DC voltage measurements to narrow down the problem.
1) Connect your handheld meters negative lead to chassis ground.
2) With Battle Short OFF start the generator.
3) Verify that inside the three relays that only the rightmost one has its internal LED illuminated. Is it?

While holding the Contactor switch UP measure the DC voltage at the following points in the following order.
a) S5-5
b) S7-8
c) S7-9
d) K15-8
e) K15-12
f) K12-4
g) K12-12

Post the DC voltages at each of them. They will be either about 0 volts or about 24 volts.
Also answer to question 3.

Here are the terminal layout for the relay sockets. Same layout for K12.
View attachment 883912
-

Here is what I've got.
K15 LED is on
Voltages as follows, in DC. Contactor held in the closed position

a) S5-5 (28V)
b) S7-8 (28V)
c) S7-9 (0V)
d) K15-8 (0V)
e) K15-12 (3V)
f) K12-4 (0V)
g) K12-12 (29V)

Thank you for the help, do you think it's a bad relay or inverter?

 

[kloppk]

Based on those readings it would look like the problem is inside the Inverter.
Specifically, there is a Solid-State Relay (SSR) K8 inside the Inverter isn't "closing" to enable the contactor to close and send power to the lugs.
The problem could be with K8 or the circuitry in the inverter that tells K8 to "open" and "close".
The K8 part number is: AQV251
The part is available from Mouser Electronics should you like to try and replace it.
AQV251


Your last reading is an error. K12-12 is tied to ground.

The SSR's on the "main board". The K numbers on the board do NOT match the K numbers in the TM.
I could figure which one is K8 on a dead board here if you choose to try and replace it.

 

[bcheval]

Based on those readings it would look like the problem is inside the Inverter.
Specifically, there is a Solid-State Relay (SSR) K8 inside the Inverter isn't "closing" to enable the contactor to close and send power to the lugs.
The problem could be with K8 or the circuitry in the inverter that tells K8 to "open" and "close".
The K8 part number is: AQV251
The part is available from Mouser Electronics should you like to try and replace it.
AQV251
View attachment 884556

Your last reading is an error. K12-12 is tied to ground.

The SSR's on the "main board". The K numbers on the board do NOT match the K numbers in the TM.
I could figure which one is K8 on a dead board here if you choose to try and replace it.
View attachment 884557

Is it possible to buy a new board or send mine out to be repaired?

OR just buy a new inverter?

 

[kloppk]

It's extremely hard to find working inverters for sale.
I've never seen just the main board for sale.
I could replace the SSR for you but no guarantee it's not another problem with the board causing it not close.
@Dewie38 may have something though.

 

[bcheval]

I hate to overlook the obvious but when the unit starts you are showing AC voltage on the meter and do you have voltage at the convenience outlet?

Yes sir and at the slave outlet

 

[bcheval]

It's extremely hard to find working inverters for sale.
I've never seen just the main board for sale.
I could replace the SSR for you but no guarantee it's not another problem with the board causing it not close.
@Dewie38 may have something though.

Dewie, what do you think?

 

[kloppk]

Something you should check is the AC voltage across terminals A & B on the Governor Controller behind the gauge panel.
Do this with the engine running and no load applied.
At no load the AC voltage should be about 178 volts AC. If your meter can measure frequency the AC frequency across those terminals should be about 254 Hz.

 

[Dewie38]

Sounds like a bad inverter.
Like I said we never repaired the inverters just replaced.
I have no internal parts for it, I do have a brand new in the box inverter and I also have a 50 hz inverter that I cranked the freq. pot up to 60 hz.

 

[bcheval]

Sounds like a bad inverter.
Like I said we never repaired the inverters just replaced.
I have no internal parts for it, I do have a brand new in the box inverter and I also have a 50 hz inverter that I cranked the freq. pot up to 60 hz.

Dewie,
Are you interested in selling them?

 

[bcheval]

Something you should check is the AC voltage across terminals A & B on the Governor Controller behind the gauge panel.
Do this with the engine running and no load applied.
At no load the AC voltage should be about 178 volts AC. If your meter can measure frequency the AC frequency across those terminals should be about 254 Hz.

Here is what I have.
AC Voltage @ A, B & C = 125V Each
293Hz Each