Redux: MEP 803a no power to main lugs

rtrask

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I have very similar symptoms to this thread: MEP 803a no power to main lugs

My generator is not outputting any current at the main lugs but is at the convenience receptacle as described on the above thread. I believe that it was putting out current at the main lugs last spring after I got all the issues with the diesel engine ironed out and the engine continues to run well. I never put a load on the main lugs. I just measured the values with my multi-meter, and it seemed correct.

The genset sat through most of the summer fall and winter, with sporadic short periods where the convenience plug was used lightly. Last weekend I needed the power for an air compressor out on my off grid property, and there was no power on the main terminals. Where the generator sat is at 8000 ft in a high desert setting in Colorado. It was exposed to the weather which included cold, wind, snow, common to that elevation and location. I guess it is not a surprise that issues arose with it sitting so long.

Light In the Dark offered this advice to the previous poster:

Do you have a can of contact cleaner? If not, consider getting some for your stockpile. Corrosion in the open element switches on these machines is a real thing, and can definitely cause what you are experiencing. I think you should start (when the machine is off) flipping the load switch on and off as many times as you can do without going mad. If there is any corrosion in this, you may free it up and cause a connection to be made again. The same could be said for the main phase switch behind the gauges... always when off. Any connection that can corrode, will corrode over time.

I don't understand the above post. What are the "open contact switches"? What is the "load switch"? The main phase switch I understand, and it is noticeably stiff, so that may be the culprit, the starting switch seems stiff to me too. I doubt that just switching the phase switch back and forth is the best approach to freeing it up. Should I pull these switches and try to give them a through cleaning? Should I go through all of the relays and clean them. What is the best order of maintenance I should follow to diagnose and fix my issue?

Guyfang responded as below.
The best thing to do, is start your own thread. That way, people do not confuse what you write and what has been written by someone else. Starting with a clean slate makes it easier for you and us to help you through this.

I do not think your elevation has an impact on the problem.

When I write advice here, I will almost only use proper terms. I rarely say start switch. I saw S1, or instead of Emergency Bypass switch, I say S7. Shorter, and its exact. So If you haven't downloaded the TM's, and maybe read the operators TM, and or looked at the wire diagrams on the doors, it may be a bit confusing for you.

The symtoms you describe sound like you can not get K1, (AC Circuit Interrupter Relay) too close. Lets not go any farther here, as TWO threads is even worse then trying to hook your problem onto someone else's problem.
I only mentioned the elevation to give the reader an idea of the extremes of weather the genset experienced. I do not think there is any issue in running at 8K feet. I have downloaded the TMs and the trouble shooting pdf as well. LITD seemed to be providing good advice a s Guy fand noted in a previous post, but I could not translate the terms he used into actions I was certain of.

trouble shooting pdf
 
Last edited:

kloppk

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If the set sat unused for a long period of time corrosion may have crept into the various switch's such as S1, S5, S6, S8 and others.
"Exercising" them with the set NOT running can help with any contact issues. Better yet spray contact cleaner such as Deoxit into the switch openings, if possible, to help clean the contacts while exercising them. This can solve some problems.

With the S10 set to NORMAL and S1 set to PRIME/RUN and engine NOT running self test DS7, the Contactor Closed lamp, to see if the lamp is good.
Press on the green lens of DS7 to do the self test. It should illuminate when pressed. If that's OK then...
Start the set and then HOLD S5 in the CLOSE position. Does DS7 illuminate? It's suppose to. When you release S5 does DS7 remain illuminated? It's suppose to. If DS7 remains illuminated when you release S5 and you DON'T have power to the lugs then it's top to take the top cover off to access K1.

Report back with your findings when you get a chance.
 

Guyfang

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So we need to begin work. In both the gen set, and meanings and terms.

Remove the rear top and control panel cover from the set.

Start the gen set, normally.

Let it run a bit.

Then just to be 100% certain, test for 120 VAC at the J1, (120 VAC outlet). You have before, and said you measured 120 volts, but troubleshooting is an orderly, step by step process. Others that follow you, may not have taken that first step. You should get 120 VAC. That means your main generator is good, and puts out correct power.

Then flip up S5, (AC Interrupter Switch) and you should see the DS7, (AC Interrupter Switch Light) come on. Did it light up? If so, measure for AC volts at the L1, L2 and L3 lugs, to the Neutral output lug. What did you read? The output depends on what position the S8 (Reconnection Switch) is in, but right now, we just want to know if you get anything.

If the DS7 is on, you should get something. We will figure you get nothing, as you said you had resumed before. But TEST anyway. If you get nothing, then the K1, (AC Interrupter Relay9 is not closing.

Now we get to why you removed the top. Behind the control panel is another space. We call it the AC output compartment. To the left is K1. If you are uncertain about what a part is called, look around where its mounted. There is 99% of the time, something written. Like K1.

Shut the set down. There are two terminal covers on the K1. remove them. or not. Its safer to remove them, but if you feel at home testing AC voltage, (and I don't know if that's the case, so I tend to say, "Safety First!) leave them on. One side of the K1 should have the terminals A1,B1 and C1. That's the input side. The other side is A2, B2 and C2. Start the set. Flip up S5. If DS7 is lit, set your MM, multimeter to AC volts, and measure from ground to A1, B1 and C1. Get voltage? Good. If so, measure from ground to A2, B2 and C2. Got voltage? I assume no.

If DS7 lights up, that means the K1 has closed. Thats the only way the contacts will allow the DS7 light to come on. So if DS7 comes on, and you have no output at the A2, B2 and C2, then the K1 is partly working. If you do NOT get a DS7 light, the K1 is not closing at all.

So, let give you time to do this stuff, and then we will know what to do from there.
 

Walter J Riedel

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I am having the same problem. My generator worked once and then nothing. Changed K1 but still the same. Could it be the relay? Also when I switch the a/c circuit interrupter up the alternator belt slips for a few seconds then stops but no light up at switch. Any suggestions?

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Ray70

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I would follow the TM and test the control wires going to K1 from S1.
The TM explains how to ( with the gen off ) run a temporary power and ground to activate and test K1.
If K1 tests good, check for power and ground to trigger K1. It's a very simple circuit to test.
If that fails, check proper functionality of the S1 switch.
If the switch tests good, then I would suspect a faulty overload relay and test it from there.
I like to start at the end point and work backwards to see where things go from FAIL to PASS... then you know where the broken point is!
 

Ray70

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Sorry... Not S1, I meant S5, the circuit interupt switch.
As mentioned above, if you hold S5 up do you get power and a green light on DS7 indicator light?
If yes, then your K1 and wiring are good but either the S5 ( possibly it's jumper diode also ) is bad, or the overload relay is bad.
 

Walter J Riedel

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Holding the S5 up does not illuminate the green light nor power the terminals. Convenience outlets have power and gauges show normal power generation. Could the K15 relay be bad?

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Guyfang

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It would be best for you to start your own thread. You are on the tail end of a dead, (more or less) thread. Better exposure with your own thread, and easier for folks to follow.

Do you have all the TM's down loaded?
Is this gen set new to you.
Do you have and know how to use a DMM, (multi-meter)
Can you read/understand the wire diagrams?
 

adcomp

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Awesome description. Mine had the same issue and this helped me debug to an issue with a wire going to K1! Thanks!

So we need to begin work. In both the gen set, and meanings and terms.

Remove the rear top and control panel cover from the set.

Start the gen set, normally.

Let it run a bit.

Then just to be 100% certain, test for 120 VAC at the J1, (120 VAC outlet). You have before, and said you measured 120 volts, but troubleshooting is an orderly, step by step process. Others that follow you, may not have taken that first step. You should get 120 VAC. That means your main generator is good, and puts out correct power.

Then flip up S5, (AC Interrupter Switch) and you should see the DS7, (AC Interrupter Switch Light) come on. Did it light up? If so, measure for AC volts at the L1, L2 and L3 lugs, to the Neutral output lug. What did you read? The output depends on what position the S8 (Reconnection Switch) is in, but right now, we just want to know if you get anything.

If the DS7 is on, you should get something. We will figure you get nothing, as you said you had resumed before. But TEST anyway. If you get nothing, then the K1, (AC Interrupter Relay9 is not closing.

Now we get to why you removed the top. Behind the control panel is another space. We call it the AC output compartment. To the left is K1. If you are uncertain about what a part is called, look around where its mounted. There is 99% of the time, something written. Like K1.

Shut the set down. There are two terminal covers on the K1. remove them. or not. Its safer to remove them, but if you feel at home testing AC voltage, (and I don't know if that's the case, so I tend to say, "Safety First!) leave them on. One side of the K1 should have the terminals A1,B1 and C1. That's the input side. The other side is A2, B2 and C2. Start the set. Flip up S5. If DS7 is lit, set your MM, multimeter to AC volts, and measure from ground to A1, B1 and C1. Get voltage? Good. If so, measure from ground to A2, B2 and C2. Got voltage? I assume no.

If DS7 lights up, that means the K1 has closed. Thats the only way the contacts will allow the DS7 light to come on. So if DS7 comes on, and you have no output at the A2, B2 and C2, then the K1 is partly working. If you do NOT get a DS7 light, the K1 is not closing at all.

So, let give you time to do this stuff, and then we will know what to do from there.
 
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