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Open neutral?
I just purchased a 1991 Marathon. I did so with the
Knowledge that there were some electrical issues with the coach. I know it will
be a pretty long post I apologize in advance. I think I have read just about
every post on this site. I am very impressed with the vast amount of knowledge
that is relayed here and would like to thank the people that manage the site as
well as those who participate.The first thing that I realized was that the coach had no
120 volt power (on generator) unless there was a 240 volt device running
(cruise airs or cooktop). As soon as I turned one of these on, 120 volts was
restored to the inverter inputs, the refrigerator and convenience outlets etc.
If I turned the 240 device off no 120 anywhere.I then plugged into 240 50amp and seemed to have full power
everywhere. I took the covers off of the Shore power disconnect and noticed a
tiny bit of arcing. I shut the power off and removed the breaker to find the
bus bar that the breaker snaps into was burned on one leg. I remove the breaker
block and orderd a new one. I wired an external 40 amp breaker box that I had
to temporarily isolate the problem. The shore power is now working as intended.
After this I checked the generator function and as before I
have to turn on a 240 device to get the 120 circuits energized. However after
fixing the breaker block short, I only have to turn on the 240 load
momentarily. I can turn on a 240 device and then shut it off and the 120
circuits remain energized.I have surmised that the inverters are toast because they provide
pass through power and go to charge mode with no problem. When switched to
invert (no AC power provided) the invert mode light goes on for about 5 seconds
and goes off. I talked to Promariner tech support and they said that they could
repair them or send me new ones at a reasonable price. I have decided to
reserve any action on replacement until I get the possible open neutral on the
generator power because it is likely that this is what ruined the inverters. I have the inverters removed and will tie the
input and output lines together for testing purposes unless otherwise cautioned
not to do so.After reading all of the related electrical posts on PC it
seems that I have a neutral contactor that is faulty. I do know that the ATS
switches both the neutral and the 120 volt legs. Why do I have a neutral on
shore power but not when powering from the generator unless running 240? Could
the breaker contact problem have contributed to this condition? I am pretty
good at troubleshooting I just need to be prompted a bit from this point. I can
provide photos and schematics if anyone is interested in diving in that far.I live in Michigan and it seems service providers for these
coaches are almost nil here. I did contact Panterra in Holland Michigan and
they indicated that they didn’t work on other coaches but recommended Holland
Motorhomes. Does anyone have any experience with them? If I can’t figure this
out I may have to give them a try. Thanks in advance for any insight anyone can
provide. JeffJeff and Lindsay
91 Marathon XL -
25 Replies
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I guess the clubhouse is full.
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Didn’t have a Marathon but an all electric coach and Seems like I had a simular problem years ago and ended up the breaker box where gen set electronics tie in finally smoked itself. Had to have a new box and internals put in. At the same time they installed a Magnum Inverter in the Puppy also. Sounds like it’s gotta be linked to the transfer switch but mine was okay. That was 5 years ago and so far so good. Hope you get it figured out. The problems on these can be frustrating for sure when most RV shops haven’t a clue.
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ck first with all power disabled look for any signs of doscoloration/over heat around terminals of switching gear. Now observation- sometime a tired breaker of transferr switch will go ahead and work with a power surge. what happens with age is springs become soft and contacts become pitted or burned/have been overheated. You can be a parts changer and start with transfer switch or figure it out your self with a multi meter. No one ever wants to comment on elect problems so please don’t take this as anything except basic info/a place to start. I often call them ghost!!!!
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What you are seeing is not a typical open neutral issue. Turning on a 240V device does nothing to restore a neutral because a 240 V device does not use the neutral wire.
If you had an open neutral, turning on a 120v device would get you some strange voltage on the 120V split phases. Voltage would depend on the actual impedance of your 120V devices that are turned on, could be anywhere between a few volts to almost full 240V. But that is not what your are seeing.
It is interesting that turning on a load wakes up your 120V legs. Almost seems like the inverter is idle mode where it searches for actual loads before it turns on. Loads below a certain wattage (eg. 40W) will not wake up your inverter. Thus when you use a DVM it will show no voltage.
Did your coach come with the Marathon manual? There should be an electrical overview diagram that shows how generator, inverters and shorepower are connected. It is not as straightforward as one would think. I can dig out my diagram but it is from a 1999 coach. You could always call Marathon to send you your diagram.
Gerald
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Thanks for the replies guys. I apologize for being impatient. I am feeling a bit of pressure because I have the inverters removed and do not want to risk running down the 4k worth of new house batteries that came with the coach. I am running the engine for about 1/2 hr per day to minimize this. I am turning off the coach and chassis battery swithces in between because there is definately a fantom draw on both systems which I know I can track down after I get this part figured out. I understand Glens point about people not wanting to comment on electrical problems especially when they have no sense of the members ability. Just to shed some light on this I have a been doing my own electical work for years including new services and change outs. I am also fairly proficient at control wiring as long as it involves switches and contactors and not diodes and resistors or circuit boards. Electrical schematics are like decifering chinese to me.
Taking suggestions from Glen and Robert I took a close look at the “Lyyght power systems” transfer switch and notice that there is a small circuit board in there with a burned diode. (small striped thing with a solid silver wire coming off each end) I think diode or maybe resister. The company still exists and seems the same model number of transfer switch is still available. I talked to the tech guy there and he is checking per my photos that they have a direct replacement unit. I am no where near too proud risk being labeled a parts changer Robert. ;)I will be swapping out this transfer switch unit if its available.
To Geralds comments- This is an interest thought that you have about the neutral not being restored by turing on a 240 device and rather its the high wattage load that may be restoring it. I assume you are referring to the pass through mode on the inverters on this. It handn’t occured to me that most if not all of the 120v circuits are running through the inverters. Can anyone verify that removing the input and output (30a 2 wire with ground) lines from the inverters and connecting them together would be fine to do in general.(barring any issues that are sending current in an incorrect path) This would be the easiest way to check Geralds hunch. My only problem with this possible diagnosis is that I have full 120v pass through power through the inverters on shore power. But not on Generator.
I will be filling in my profile thoroughly and properly introducing myself. I apologize for not doing that first. Thanks guys.
Jeff
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The inverter turning off after 5 seconds could be because it is entering “sleep” mode because it did not detect any loads. Easy to test though. Either disable “sleep” mode in the config menu of your inverter or provide a mininum 100W load on each leg of the split phase. Probing with a DVM or other multi-meter will not provide enough load to turn the inverter on.
Of course, there could be other reasons why the inverter turns off, e.g. battery. I assume you have made sure that the house battery has adequate charge and can deliver the amps the inverter needs. How did you test the house battery bank? What was the house bank voltage while it was trying to invert for 5 seconds?
Jeff and Lindsay
91 Marathon XL -
Thanks Glen. I have an update on my problem. I found a #10 control wire in the transfer switch enclosure that had a bad crimp on the spade terminal. Someone had crimped it with the tools crimp pin toward the split side of the connector sleeve. It was loose and making poor contact. Its amazing how even some professionals do not know the proper way to crimp terminals. Anyways,I fixed that and fired up the generator and everthing seems fine now. I am however not entirely certain that this was the issue.. To test the fix I wired the input and output of the inverters together instead of reinstalling the inverters. I did test the inverters without the coach AC power in play. (20 amp cord on the iput and 100 watt light wired into the output). No luck there. I will install the inverters back into the coach tomorrow just to verify that they are not functioning. The batterys are holding at 25.1 volts at rest with no charge input. The PO told me that he had installed new coach batteries last summer but he couldnt produce an invoice. Is it possibel that a battery bank that is at 25 volts will not fire up a 100 watt bulb through the inverters? Do I need to unhook and load test them? I want to thank everyone for the help on this. This group is amazing. I am a new Prevost Owner and I am not sure how much I will have to offer here immediately but I sure hope I can help others in the future. Jeff
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Oops. Thanks Gerald for the last post. I will also check the battery voltage during the 5 second invert indication period to see if it is trying to load the batteries. I think that is what you were asking.
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Please put a signature in “Profile” so folks know what year and conversion you have without trying to find it on the fist post.
If if you have Lifelines, there will be a white round sticker on the batteries with 2 letters. I can give you the manufacturer date with those letters.
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No problem Tom. Lindsay just filled in the profile.
I have the 10 of the generic type ub12 batteries. From reading here it looks like the Lifelines are the best option when we have to replace them. I appretiate the offer and will be checking the date codes to see what we have for age on them. Regards, Jeff
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Jeff,
Everyone wants to help, and had I not been out of service for 2 days I probably would have jumped in, but I am getting a strong sense your coach is not a “virgin”. You either have multiple issues going on strictly due to an electrical or mechanical failure (I’m not a big believer in coincidences) or you have a coach someone monkeyed around with. If that is the case someone with feet on the ground (and not trying to help over the internet) should be working to follow the power through your house systems from the origin which could be inverter, shore or generator.
Your description of some of the things you found sound too much like shoddy terminal connections and possibly maybe some creative license applied along the way. Marathon did not do a lousy job on building your coach. They had tight connections and well applied terminals. The technology of the vintage was fairly basic so some of what you describe does not make sense.
I would strongly urge you to seek assistance from Marathon in finding out how they originally set up the coach, and then verify things are that way, or as an alternative, if it is driveable get it to someone like Jeff at ETLC to sort things out. I am very concerned about your safety right now because you can get hurt if the electrical system does not have continuity on the circuits.
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Jon,
Thanks for jumping in on my situation. The first thing that I did when getting the coach home was go through the huge stack of manuals and documents that came with the it. During this process I went throught the coach and tried to familiarize myself as to how everything was suppose to function. You are correct in your hunch that someone has “monkeyed” with it. In the electrical diagrams provided by Marathon I discovered that the transfer switch control wiring had been altered. There are a couple of very small reconfigurations that have been noted on this transfer switch schematic. After spending 5 full days reading inspecting and testing this is the only thing that I think has been altered. The rest of the coach truely seems to be original mechanically and furnishings wise. Knowing that my inspections and research start with limited experience with luxury coaches, I agree with you that having it gone over by an expert such as Jeff at ETLC would be a wise venture. Also from reading here Jeff would probably be the best choice because of his reputation and also he is probably the closest qualified shop geographically for me.
As noted in an earlier post to Gerald, the only things I have done is change the shoreline breaker block and breaker and changed the 3 spade terminals that seem to be linked to the alteration. I believe that the control wiring for the AC power is working as intended now. The only exception would be that I have yet to test the auto start function on the generator. If this does not function by simply switching it to autostart mode and bring the batteries down with 24 volt loads I will wait and have it tested by Jeff.
I appreciate your concern and have a bunch of respect for you from reading your posts. Rest assured knowing that I have kept myself out of trouble “for the most part” for 30 years working on things in which I have limited knowledge. The key here as you know is not doing anything that your are unsure of based on ample research. Its important to be able to be able to sort out if a task is better left to an expert. There is also much to be gained by understanding the systems before bringing something to an expert so long as your actions do not cause additional problems. I have no illusions that there will be no more problems found or that I will be able to diagnose and fix anything and everything on this coach.
Thanks again Jon! Jeff
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It is very difficult for anyone to diagnose some problems when nothing seems to fit within logical parameters.
It is far worse trying to do the diagnosis over the internet. When at the coach I suspect all of us that try to diagnose problems surmise what might be the cause, and almost without thinking we check for continuity, or voltage, or air flow or movement, or any of a million other things that might sharpen our focus, and help isolate the problem.
But I think when an owner or previous owner has made a change, and especially if the change is either not obvious, or just plain makes no sense, we all go a little crazy until we can figure things out. I still have a very hard time trying to include unexpected causes for issues. One I will never forget was in dealing with a very smart owner trying to diagnose a problem on a coach that was brand new to him. He had just bought it and realized he could not get a certain function to work on the leveling system.
He and I talked through the entire operating logic of the system and the only explaination of why he could not get the coach to do something was a defective valve. Everything else we could consider was checked and verified as operational. As it turned out the reason the feature was not doing what it was supposed to do was the pneumatic system was water logged. Not just a little moisture, but a full hydraulic lock that prevented the device from doing what it was to do. Neither of us got our brains wrapped around a pneumatic control system filled with water because it was so far from what was expected. I thnk the exact same thing may be at work creating your problems that have no logic based on what we understand a converter’s system operation will be.
Air is pretty safe to play with and under a worst case you may create a leak. Electric is not so safe, especially if you have reverse polarity or no ground. At the very least verify you do not have a “hot” chassis where you become the conductor of electric if you touch the chassis or any metal parts.
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I suffer from the same affliction. I tend to go in denial when a problem does not turn out to be what I think it is. I usually move on eventually but not until the dead horse is beat sufficiently.
I did test the skin and frame with a multimeter to a ground rod. (0 volts during generator and shore operation respectively) Thanks for the heads up on that!
I know the changover and AC system is working like it is suppose to when I wire past the inverters. With the invers wired in , pass through power works fine when I am on shore but the inverters do not like the generator power for some reason. I tested the input at the inverters (on gen power) and its 121 volts with a good neutral and ground. But the inverters do not want to pass it through. Im wondering is a frequency issue with the generator. I cant understand why the inverters reject pass through on gen but not shore when the voltage is the same in either case. I sent the inverters in today and will see what they find before doing anything else. If they say the inverter is fine I will throw a frequency meter on the gen power. I will probably make the trip to ETLC if this doesnt start making sense to me after inverter tech findings. I will report back with details after this is fixed.
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I am not a Marathon expert so take the follwing with a grain of salt.
Depending on how the converter set up the electrical system, air conditioners may not go through the inverters. I am not saying that is true on yours, but before you go much further I think your first step is to find out how Marathon has set up the 120V circuits. The inverters and circuits have evolved since inverters were first used by converters and in some conversions you could not operate a house Cruiseair or roof AC via the inverter.
If your coach has non-original inverters that may add to the mystery for two reasons. The installer may have changed the circuitry, or the inverters may not be able to handle the load of an AC unit, especially on start up.
If your coach has over the road air (Prevost installed) it may be you cannot run AC through inverters.
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