MEP 004a stuff I couldn't find by searching

[deuce bigalow]

Ok so the frequency issue was caused by incorrect rpm, I got that dialed in now.

I was able to run a drill motor off the convenience receptacle.

The circuit breaker indicator will not illuminate when I hold the circuit breaker switch up, but it lights up when I push the light in to test it. So the indicator is good but mabey the switch or the breaker is bad?

I tried hitting the test/reset to reset the reverse power indicator but it didn't work. The reverse power indicator will go off temporarily if I hold the start switch up while running.

 

[sewerzuk]

OK; after the set is running, place the battleshort switch in battleshort. Then try to close the main breaker again. Let us know if it closes or not.
This will help to prove if the main breaker is working, and if there is a problem with the reverse power alarm circuitry...

 

[PeterD]

The circuit breaker indicator will not illuminate when I hold the circuit breaker switch up, but it lights up when I push the light in to test it. So the indicator is good but mabey the switch or the breaker is bad?
...

I would suspect that the safety circuit is disabling the main contactor, which is why it does not engage when the switch is pressed up. I doubt the switch is bad (could be but I don't think so.)

Do the Battle Short test as Sewerzuk says, that will help diagnose perhaps.

 

[deuce bigalow]

Ok, I did the Battle Short test and nothing happened.

 

[sewerzuk]

Ok, I did the Battle Short test and nothing happened.

Not doubting you in any way, just wanting to make sure we're on the same page (hard to tell exactly what is going on when I'm not there in person watching things happen):

1. You started up the generator with the battleshort switch in "off" (shouldn't be able to start it with the BS switch in "on), and brought it up to proper frequency and voltage

2. You closed the battleshort switch.

3. The red battleshort light came on

4. You attempted to close the main breaker by momentarily holding the switch in the close position

5. The main breaker indicator light did not come on

If you did perform the above 5 steps as I described, I have a few more questions/things for you to test:

*be careful while doing this; there are quite a few exposed terminals with line voltage on them while the generator is running. Don't leave any loose or uninsulated tools on top of the generator, inside of the genset, etc. while you are working. Also be careful not to brush anything with your hand, elbow, etc.

1. After you perform the battleshort procedure above, test the output at L1-L3 (either with a DVOM, or some kind of load). Expecting 120v from each line to L0 (neutral), and 208v from line to line. Sometimes the aux contacts in the main breaker don't work, even though the breaker does close.

2. With a DVOM, test the input side of the main breaker (it's the black box on the upper left side when you open the door, above and to the left of the L0-L3 output terminals). The input side of the breaker is on the right, as you are facing it. You should get 208v from each line to line.

The reason we are doing this is that your main breaker SHOULD close with the BS switch closed, regardless of whatever alarms are locked in. We need to figure out why it isn't indicating closed...once we get past that, we can begin to work on the reverse power indicator.

This isn't the exact method I would use for troubleshooting if the set was in my shop, but I think if we can gather enough symptoms we can figure out what the problem(s) is/are.

 

[deuce bigalow]

Not doubting you in any way, just wanting to make sure we're on the same page (hard to tell exactly what is going on when I'm not there in person watching things happen):

1. You started up the generator with the battleshort switch in "off" (shouldn't be able to start it with the BS switch in "on), and brought it up to proper frequency and voltage

2. You closed the battleshort switch.

3. The red battleshort light came on

4. You attempted to close the main breaker by momentarily holding the switch in the close position

5. The main breaker indicator light did not come on

If you did perform the above 5 steps as I described, I have a few more questions/things for you to test:

Yep I did 1-5 and the main breaker indicator light did not come on.

1. After you perform the battleshort procedure above, test the output at L1-L3 (either with a DVOM, or some kind of load). Expecting 120v from each line to L0 (neutral), and 208v from line to line. Sometimes the aux contacts in the main breaker don't work, even though the breaker does close.

Using a multimeter I am not getting any reading from any of these terminals. Sunday I am going to try wire brushing them and check again with a digital meter. I only had a few minutes on Saturday to tinker.

2. With a DVOM, test the input side of the main breaker (it's the black box on the upper left side when you open the door, above and to the left of the L0-L3 output terminals). The input side of the breaker is on the right, as you are facing it. You should get 208v from each line to line.

I am however getting voltage across the main breaker.

Could the issue be in the tactical relays? I thought a bad relay would mean no voltage reading across the main breaker?

Thank you very much for all the troubleshooting help.

We've had 3 power outages already this year- I hope I can get this generator working.

 

[sewerzuk]

I am however getting voltage across the main breaker.

Could the issue be in the tactical relays? I thought a bad relay would mean no voltage reading across the main breaker?

Thank you very much for all the troubleshooting help.

We've had 3 power outages already this year- I hope I can get this generator working.

It just means that the main breaker isn't closing.
The tests you did prove that it isn't just an indication problem; the breaker actually isn't closing. It should close with the battleshort switch on, regardless of whatever alarms are occurring.

I'll take a quick look at the schematic later today and come up with your next test...I'd like to find out if the breaker is receiving the "close" power from the switch. This will tell us if the breaker itself is bad (I have had 2 bad breakers in about 25 sets that I have repaired, so it isn't all that uncommon).

We're ignoring the alarm light for now...won't do any good to fix that if the main breaker won't close!

 

[sewerzuk]

OK; I just got done troubleshooting an -004a with a main breaker that would not close so I'm now VERY familiar with the circuit! A concrete construction company was using the set to power their site and the main breaker would intermittently open during operation and then not close again; tracked it down to a loose TB connection inside of the special relay assembly. So...we'll get yours figured out now!

I'm using the AC schematic diagram on Page 345 of TM-9-6115-464-12. Might help for you to pull it up so you can see what we're testing. Basically, S3 (breaker open/close switch) sends 24v through a series of relays (overload, short circuit, etc.) to the main breaker. The battleshort switch (S7) bypasses all of those relays, except for K13 (short circuit relay). So, we're going to test to see where that 24v is being lost.

1. First question; is your set a precise or utility set?
There are several ways to tell, but the most relevant way is to look at the special relay assembly (the largest box with all of the plugs/harnesses coming out the top). One of those plugs should have a shorting cap on it; J31. If the shorting cap is in place, it is a utility set. If there is a wiring harness plugged into J31, it is a precise set. (there are other ways to tell, too)


2. We'll start with an easy test first...Place the main generator switch in "run" (do not start the generator). Place the battleshort switch in battleshort. Hook a voltmeter (VOM) up to the main breaker switch; + lead to terminal 5 (very bottom terminal, on the right hand side of the switch), - lead to a good ground. If you're having a hard time finding the numbers on the switch, the wire leading away from that terminal should start with "P57A". Hold the switch in the "close" position. You should see 24v on the VOM. If you don't see 24v, you need to work upstream. If you do see 24v, you need to work downstream.

A good practice is to check your VOM first before taking measurements to make sure it will read 24vdc, so you don't get a false negative reading. TB1-5 should be a good place to get 24v.

Let me know the result of the voltage test; I'll come up with the next test for you after that.

 

[deuce bigalow]

Ok I finally found some time to work on this generator today.

To answer the first question it is a utility set.

I did the test on the main breaker switch and terminal 5 to ground produces 23.0 volts when I hold the switch in the close position. I also tested the DVOM on the battery terminals and have 24.9 volts.

So I am studying the wiring diagram on page 345 of TM-9-6115-464-12 and I am having difficulty finding S3. I have found S2 the start switch and S4 the panel light switch, but I can't find S3.

 

[sewerzuk]

Uploaded a copy of p 345; highlighted S3 in blue. Highlighted in red the circuit path from S3 to the main breaker that we will be testing. Should help you find it on your schematic...

Next test:

Your main breaker switch is sending the necessary 24v; let's find out if it is getting to the main breaker and, if not, where we're losing it.

The battleshort switch bypasses all of the safety relays except for the short circuit relay (K13). So, lets test to see if power is getting there.

Pull P51 out of J51 (this is the plug on the Tactical relay box, on the left side of the generator, just below the main breaker)

On the plug that is at the end of the now loose wiring harness, locate pin "b". Plug the + terminal of your VOM into that terminal, and the - to a good ground.

Turn the main generator switch to run, the battleshort switch to battleshort, and hold the main breaker switch in close. You should see 24v on the vom.

If you do not see 24v, you need to work upstream (P50, P2, P1). If you do see 24v, you need to work downstream (P50, P10, P41). Keep in mind that, if you pull P2 or P1 you cannot test for voltage because power to the main control panel passes through this plug and nothing will work with it removed (although you can check resistance/continuity).

The set that I just repaired had a loose connection at TB101-20, in the special relay assembly (where the battleshort switch ties into the main breaker circuit).

 

[deuce bigalow]

Thanks again sewerzuk for all the help.

Today I did the test on P51, pin b and got 23.8 volts.

Sounds like I should take a look inside the relay enclosures... and it could be something as simple as a loose connection on a terminal board?

 

[sewerzuk]

The next place to test would be the circuit breaker itself; remove the plug, find pin A, and do the same test (main switch "on", battleshort in battleshort, main breaker switch to close). If you get 24v there, the breaker itself is bad...if you don't, then it is either a connection at one of the plugs (J10, J50, J51) or the Short circuit relay (K13) in the tactical relay box. Should be pretty easy to track down now...

 

[deuce bigalow]

The next place to test would be the circuit breaker itself; remove the plug, find pin A, and do the same test (main switch "on", battleshort in battleshort, main breaker switch to close). If you get 24v there, the breaker itself is bad...if you don't, then it is either a connection at one of the plugs (J10, J50, J51) or the Short circuit relay (K13) in the tactical relay box. Should be pretty easy to track down now...

I did this test on pin A of the J51 connector and got 0.0 volts.

I also fired it up and ran it for a few minutes today and changed some coolant.

The reverse power indicator is no longer lit up when its running.

I think it was lit up for a minute then it went off and has never come back on.

 

[sewerzuk]

I did this test on pin A of the J51 connector and got 0.0 volts.

I also fired it up and ran it for a few minutes today and changed some coolant.

The reverse power indicator is no longer lit up when its running.

I think it was lit up for a minute then it went off and has never come back on.

Well, move your way back toward the tactical relay box (P50, J10). It's either one of those plugs, or a loose connection/bad short circuit relay K13.

 

[stampy]

Not to hijack but what type alternator (model) is supposed to be on this unit My genset has no alternator for charging and they cut the cables to it and the starter. I looked for the TM here (so I could rewire what they cut) but couldn't find the one for mep 004.
Thanks to Peter D for helping me locate a starter. Now on to the alternator, fuel cap and dipstick!