MEP-803 panel dead after replacing batteries

[uniquify]

A month ago, I noticed that the 803 at my in-law's ranch was slow to turn over when the air temp was below freezing. The batteries were 6 years old, so I decided to replace them next visit. Later that day after temps warmed up a bit, the gen started and ran fine for about an hour.

Today, I replaced both batteries. But now I get no response from the main switch. Nothing from the panel lights either. The emergency stop switch is out. The DC breaker inside the control panel is in. The fuse below that DC breaker tests out ok. The dead crank switch is in the NORMAL position.

It acts like it's not getting power to the panel. If I bump the dead crank switch, the new batteries will turn the engine over. I double and triple checked the battery cables and connections.

Guessing I'm missing something simple, but I'm scratching my head. I have a digital multimeter with me and am in the process of downloading the TMs to their PC.

 

[uniquify]

I tested the voltage of the new batteries. One was 12.25 and the other was 11.77, so I hooked a charger to the one that was low.

 

[ROTZINGER]

Unit might be 24v, make sure batteries are in series and not in parallel

Enviado desde mi SM-G935F mediante Tapatalk

 

[uniquify]

Unit might be 24v, make sure batteries are in series and not in parallel

Enviado desde mi SM-G935F mediante Tapatalk

Yes, the batteries are in series to make 24v. After charging the lower battery, I'm reading 24.7v at the slave receptacle. No change to the panel after charging.

 

[ROTZINGER]

I would suggest finding the Tms and following troubleshooting, it's surprisingly efective!
Good luck pal!

Enviado desde mi SM-G935F mediante Tapatalk

 

[uniquify]

Got the TMs. I'll work through the ENGINE FAILS TO CRANK portion of the -24 tomorrow.

 

[Ray70]

Here's a few quick things to check:
If you are confident that the batteries are connected correctly and all 4 connections are good.
Flip on the panel lights. Do they work? If not, verify your dead crank switch is in the normal position.
Verify the circuit breaker inside the control box above the gray fuse holder is not popped out.
Verify the red emergency stop switch on the front control panel is not pushed in.
If these things all check out good, take a volt meter and check if you are getting 24V at the slave cable. if not, there is a bad connection somewhere with one of the battery cables. If you do have 24V at the slave port but the main panel is still dead we will need to diagnose further.

 

[uniquify]

Thanks for confirming my thought process. I went through most of that in my first post. Seems like something may have failed before/during the battery change.

Here's a few quick things to check:
If you are confident that the batteries are connected correctly and all 4 connections are good. Yes, verified 4 times.

Flip on the panel lights. Do they work? Tried that, no they do not work.

If not, verify your dead crank switch is in the normal position. Yes, the dead crank was in the normal position.

Verify the circuit breaker inside the control box above the gray fuse holder is not popped out. Yes, the circuit breaker is pushed in.

Verify the red emergency stop switch on the front control panel is not pushed in. Yes, it is pulled out.

If these things all check out good, take a volt meter and check if you are getting 24V at the slave cable. if not, there is a bad connection somewhere with one of the battery cables. If you do have 24V at the slave port but the main panel is still dead we will need to diagnose further. Yes, I have 24.7 volts at the slave port.

 

[Ray70]

Ok, so lets start by checking for 24+ going to the panel.
Power comes from the post on the back of the starter solenoid then goes to the MT4 charging shunt.
It then goes through the CR1 Diode and then to the dead crank switch.
From the dead crank normal position power goes to the E-stop switch, then to the CB1 circuit breaker,
I would start by checking the connection on the starter solenoid. From there, next thing I would do is check for power in and out of the CR1 diode located inside the control box, on the left rear wall below about 4 or 5 resistors.
Check that diode and see if you have 24V on both sides of it.
If you do, then check to see if you have 24V on the Comm or #2 wire on the dead crank switch.

 

[uniquify]

Thanks Ray70, I'll run through those checks tomorrow.

 

[Guyfang]

Book mark.

 

[uniquify]

Got the cattle fed before the snow began again.

Had my brother in law verify the battery cables. All was correct there. I toggled the dead crank switch from NORMAL to OFF and back to NORMAL. Then went to show him how the panel was dead, but it wasn't dead this morning...

Turned the master switch and the fuel pump turned on and the generator started up like nothing was wrong.

Best guess at this point is that the dead crank switch was not making a good connection yesterday. Messed with it for about 20 minutes before the snow started and could not get it to fail again. I verified that the wire connections were tight to the dead crank switch. Nothing was loose.

I don't like this phantom problem / fix. Hard to prove that it won't happen again at an inopportune time. But it's hard to pinpoint a problem that isn't currently happening.

 

[Guyfang]

But now you know where to start looking. If an TQG turns over with the dead crank, there is nothing wrong with the starter or K2. So very many folks start looking at the starter, and its really a robust thing. Or at the K2. Rember, if it turns over with the S10, start looking from the S10, towards the S1. Not in the other direction. Look at the schematic.