Chassis Voltage/ Over & Under Voltage Issues

[0533]

All was great when I went to TGO on Thursday. But when I returned I started to get an over and under voltage problem again.

I am still having problems with my Chassis voltage output.

Here is what I am experiencing:

When I start the bus the voltage meter reads out at around 28.2 volts.

Once I warm up the bus for a few minutes it is still ok.

The second I hit the Air Parking Brake the voltage runs up to about 30.5 and I get an over voltage. It also happens when I use the Jake Brake, but not when I turn on lights, or dash air conditioner. It appears to be isolated to the brakes. (My last visit to Prevost Car Dec. 4, 2008 they reset my ABS system which showed an over voltage)

Here is where it gets tricky: If I turn on the genset the voltage drops from 28.2 to 25.5 and stays there unless I use the Jake Brake in which case the voltage will swing up to around 30.5 wildly and then back down.,

1. Question: How is it possible to have the genset that is providing energy to the house side effect the chassis side:

Here is what the Service manager at Marathon Florida told me to do, which I did: John is a great guy and really helpful.

John (Marathon) Said to Do: The generator powers the inverters in charging the "house batteries" not
the engine batteries, the only thing in common would be the "jump start"
relay stuck on. This would allow the engine alternator to stop charging
causing the light to come on at the dash.
To test this turn off shore and generator power.
Check voltage at the chassis batteries.
Turn on house or generator power.
Check voltage at the chassis batteries and see if it increased.
Jump start solenoid is usually mounted above the engine batteries, check
both sides for voltage should be different. If the same solenoid stuck,
turn off house 12 and 24 volt house disconnect switches for 20 seconds
then turn them back on and recheck voltage.

2. Question: What possible relationship is there between the Jake Brake, Parking brake, and the ABS system, could there be a short to ground somewhere, maybe in the ABS system??? Have no clue but need to sort this out as the voltage swing is not good for the equipment.

PS> I have replaced the Voltage regulator, it is new. I am also replacing tomorrow the Vanner Monitor EM70A the little one that monitors input, balance etc, as I am also experiencing a balance issue as well, but only from time to time.

Love some ideas on this one.

Thanks,

Bruce

[Jon Wehrenberg]

Bruce, As I read the process the Marathon service manager recommends I have to concur. When you first posed this question if you will recall the jump start relay was a consideration.

However, what is puzzling is the voltage going up with the Jake or parking brake release, and with it going down with generator start.

I am not familiar with the Marathon system design so anything I say is speculation and should be treated as a guess. I am going to start thinking about this to see if I can conjure up any events that would cause what you describe. This is a serious issue, but I do not think it is impossible to solve.

[0533]

Good morning Jon.

It is certainly an odd one without a doubt and seems to be getting worse than better with the various attempts that I have made.

My system consists of a 270 Amp alternator, an Isolator, a regulator (new) 3 Vanner systems, one for each Chassis and House side and one that is a monitor that monitors the 12V, 24V, balance, etc. And of course the Jump Start Relay.

What does the Jump start solenoid that is usually mounted above the engine batteries look like??

Important maybe: While at TGO I did take off each lead to the Vanner EM70A (the little one) and clean all leads and place them back on. This wild swing of voltage really ramped up after this. maybe nothing. I will be replacing the Vanner EM70A monitor tomorrow morning, as I was told they can start to go, but have no clue what affect they could have on the system.

It is really odd that when I start the genset it will lower the voltage on the chassis side down to 25.5 It makes no sense at all to me. It stays at 25.5 as long as I do not use the jake Brake. in which case the power will swing up for a moment to 30.5 V and back down.

PS> I have the battery charger off, no charging power to the chassis batteries.

I wish I new more about what was happening. I will test anything and replace whatever to get this figured out.

It does sound a little like there might be some type of short to ground issue with the ABS or the braking system ???This of course does not answer the Gen question though.

[Jon Wehrenberg]

Still thinking here, but I have questions.

When you turn on the genset, is the engine running?

What happens when you connect to shore power under the conditions I question above, but with the genset off?

Are you reading these voltages at a display in the bus or are you taking them with a meter at the chassis batteries?

Do you have a chassis battery charger and is it turned on?

Here is what I think I know. With the bus engine running, both sets of batteries should be charging and the 28.2 volts is a good number.

If the engine continues to run, and the generator is started, that should provide 120V AC to the inverters and now they are functioning as battery chargers for the house batteries only and that charging current should not reach the chassis batteries because the two sets are isolated. However the alternator should continue to charge chassis batteries at 28.2 volts.

The inverters will charge the house batteries at the output voltage they are set up to provide based on their charging protocol.

Since the bus alternator voltage is regulated via the regulator if the engine continues to run, but the chassis battery voltage drops to 25.5 with the engine running, that tells me that the voltage regulator is sensing excess battery voltage on the circuit which is connected to batteries (or the sense circuit) and it is not providing power to the field wire to make the alternator function.

I'll wait for you response to the questions, because they are important. I wish the bus was in my garage so I could play with wires and jumpers to trace why the voltage regulator is getting mis-information in the form of high voltage on the sense circuit. (High voltage in regard to its set output, not necessarily excess voltage)

[0533]

Let me answer each question below:

Still thinking here, but I have questions.

When you turn on the genset, is the engine running?

Yes: This is all happening while I am running the engine.

What happens when you connect to shore power under the conditions I question above, but with the genset off?

Nothing, no issues at all

Are you reading these voltages at a display in the bus or are you taking them with a meter at the chassis batteries?

Yesterday while in the bus looking at the Voltage dash Chassis meter.

Do you have a chassis battery charger and is it turned on?

I do, it was turned off

Here is what I think I know. With the bus engine running, both sets of batteries should be charging and the 28.2 volts is a good number.

If the engine continues to run, and the generator is started, that should provide 120V AC to the inverters and now they are functioning as battery chargers for the house batteries only

When the gen is running this is what is happening, at least in part.


and that charging current should not reach the chassis batteries because the two sets are isolated. However the alternator should continue to charge chassis batteries at 28.2 volts.

Is it current that is getting to the chassis?? or is the genset causing some type of current drop, as the voltage actually goes down when the gen comes on 25.5V from 28.2

The inverters will charge the house batteries at the output voltage they are set up to provide based on their charging protocol.

House seems fine and charges up nicely.

Since the bus alternator voltage is regulated via the regulator if the engine continues to run, but the chassis battery voltage drops to 25.5 with the engine running, that tells me that the voltage regulator is sensing excess battery voltage on the circuit which is connected to batteries (or the sense circuit) and it is not providing power to the field wire to make the alternator function.

Jon, what is the "Sense Circuit" is this the vanner EM70A small system monitor??? Black box about 4" x 8" maybe 1" deep??

I'll wait for you response to the questions, because they are important. I wish the bus was in my garage so I could play with wires and jumpers to trace why the voltage regulator is getting mis-information in the form of high voltage on the sense circuit. (High voltage in regard to its set output, not necessarily excess voltage)

I wish it was in your garage as well.

When the over voltage occurred yesterday (when applying the Jake Brake driving along at highway speeds) the voltage would swing up to 30.5 just for a moment the blower would increase speed as well. This is with the Genset running.

When I got into the park where I leave the bus and while at idle my battery light comes on, the voltage output was 25.5V on the dash chassis meter.

I also turned off the bus to unhook the toad, and when I restarted the bus an Battery imblance light came on.

I wonder if the vanner systems monitor is acting up here or who knows. There is for sure a real voltage surge and not a false reading by the meter, this I am sure of as there is real evidence of a surge in power.

When

[Jon Wehrenberg]

Bruce,

Ignore the Vanner monitor. It does not do anything to regulate or control voltages, so for the moment take that out of the picture with respect to it being part of the voltage variations. As to the battery low voltage light and the imbalance I would say it is working because it is lighting warning lights when this goofy stuff is happening.

Let me see if I can make an off the wall statement that might resolve this. I have some concerns which I will express, but let's start here if you are willing. I assume you have a big voltage regulator that has a positive or 24V terminal, a ground terminal and a field wire terminal.

When you have the condition that drops the chassis battery voltage to 25.5, can you put a meter on the 24Volt terminal and tell me what it reads? Once I have that it may not give me an answer or maybe it will. I do want you to set up the bus so the chassis voltage is down when you get that reading.

I hope it reads some higher voltage like 30 volts. If it does I have more questions. If not it is back to the drawing board.

[0533]

Jon,

John Kincaid at Prevost Car jax just wrote asking questions regarding this issue.

Take a look at at his questions:

John K wrote:


Good morning,
Question 1 does the coach have an isolator the splits the voltage to
house and coach that would be the tie

Yes

#2 has there been any bulbs changed on the brake lights or wires rubbed
on tow connectors in rear of coach

I do have one light out

or does it have aftermarket towing
light converter for two bulb tow vehicle

Yes I do

John Kincaid
Prevost Jacksonville
Service Manager
800-874-7740 phone
904-886-0092 fax

[0533]

I will do this today and report back.

My plan now will be to run the bus, run the genset and check the 24 volt output of the alternator.

[Petervs]

Since you mention effects of the Jake Brake, air brake, and connecting/disconnecting the toad , I thing there might be something amiss in the brake light circuit.

The Jake brake activates the brake lights, as do the air brakes.

Maybe the toad wiring is sending power somewhere it is not supposed to go?

At least these things should be eliminated as causes, if nothing else.

[jelmore]

I also had wild voltage swings on the chassis side and tried (lamely) to pin it on some repeatable sequence. It would be fine for a while and then start acting up. After much diagnosis and many phone calls, it was a loose battery cable.

[0533]

Hello Jim and Peter,

Both good thoughts.

Peter your ideas reminded me that when I am experiencing the problem I am also hearing some type of beeping noise almost like a muffled backup (engine in reverse) beeping sound. I assumed it was from the Jake Brake each time it comes on, is there a audible noise from the jake brake when its applied???

I also plan on checking all lights, the tow equipment etc. It is interesting that the problem has magnified when towing. I was having some intermittent issues before, but each time I was not towing but driving without the toad behind.

Also I have completely inspected and carefully taken each battery terminal and cleaned and sprayed each secured tightly all battery terminals, all good here.

I really feel now more than ever that the jake Brake plays some role here. It is also Ironic that I had Prevost Car go into the computer and change the Jake Brake performance recently as well,????

[Jon Wehrenberg]

Peter, I agree, but where I am heading first is to find out on the low voltage side if the regulator is shutting down the alternator because it is sensing high voltage. If it is, then the issue becomes finding out what is creating the high voltage, and I think the inverters can be ruled out because Bruce said this does not happen on shore power.

What makes no sense is why shore power does not do that making me wonder if the Genset alternator is somehow part of the equation.

I suspect two separate unrelated issues happening simultaneously by coincidence. One creating the high voltage situation and the second the low voltage situation. Do you agree?

[0533]

I am now back from the bus, have done some trouble shooting, here are the results: I did however learn that the problem also exists when the Gen or the Shore Power is on it makes no difference.

All readings are with Engine running 1000 RPM.

I. Alternator Readings:

1. Alternator: Without Gen running: 28.9 to 29.1 V
2. Alternator : With Gen running 10.1 V
3. Alternator: With Shore Power on, 9.8 V
4. Alternator: Without Gen or Shore at Low Idle, but with full load, all lights, dash air, Blower motors, OTR, Jake Brake on 29.7

II. Isolator Readings:

1. Isolator Without Gen: 28.1 House side, 28.1 Chassis side.
2. isolator with Gen running: 28.8 House side, 25.3 Chassis side
3. Isolator with House main disconnect turned Off. 25.3 on Chassis side.

III. Regulator

1. Regulator without Gen on: 28.0 at FLD 27.6 At Ignition
2. Regulator With Gen on: 27.5 Fld. 25.3 at Ignition

I also checked the lights, tail lights, the tow package, all wires and bulbs seem fine at a glance.

[Jon Wehrenberg]

Ignoring the high voltage / Jake brake issue for a moment I think I understand the voltages go down when the inverters are supplied with AC power.

I do not know what alternator voltage means, but regardless of where that measurement was taken it says if I am reading it properly, when 120VAC is supplied to the inverters, either from the generator or shore power, with the engine running the chassis batteries stop receiving a charge. They are at their normal voltage when no charging current is being applied to them.

Did I get that right?

If so, the next numbers I looked at were the value of the voltage to the regulator while this was happening. I did not see high voltages that would cause the regulator to disconnect power to the alternator field because the voltage was beyond the regulator set point.

Now, for reasons I have not yet fully considered, I am thinking the isolator may be the issue. If the coach were mine, I would disconnect the alternator terminal and chassis battery terminals from the isolator, bolt them together, start up the engine and generator and see what happens to the chassis voltage.

Don't ask me why just yet that I am thinking along those lines, but by doing this there is no downside, and it takes the isolator out of the equation as a potential problem if the chassis voltage remains low with the generator running.

All I can say right now is this might have something to do with the inverters being powered. Before disconnecting the terminals and joining them it would be of value to shut down the inverter battery charger functions while the generator is running to see if that has an effect.

[garyde]

Was there any discussion about the age and type of chasis batteries. Also, have all of the cables been cleaned and checked for connections. Finally, where the ground wire from the batteries lands at the frame of the Bus, is this in good condition? It sounds to me like a ground issue.

[gmcbuffalo]

What is the battery charging voltage reading coming out of the inverter/charger?

Could one bad cell in a battery cause the inverter/charger to send a high voltage to the batteries coupled with a bad (stuck on) isolator, therefore sending a signal to the regulator to lower the voltage coming out to the alternator?

GregM

[Jon Wehrenberg]

Greg,

That is where I was going when I inquired about the voltages to the regulator, but that does not appear to be the case based on Bruce's readings.

If the chassis charging rate goes back to normal with the alternator connected directly to the chassis battery terminal, bypassing the isolator I'm thinking the isolator may be the problem (I just haven't figured out how.)

[0533]

Chassis batteries are all good, terminals have been cleaned and secure, Bus ground is clean and secure as well. The chassis batteries are good, but thanks a lot for the advice.

[0533]

I plan on doing the Isolator Test today as Jon suggested. Hope this is the problem? But if not I guess I need to consider doing the same test (at least disconnect one side) with the Jump Start Relay to remove it from the equation as well, possible bad solenoid, stuck on as well.

[Jon Wehrenberg]

Bruce,

You realize when you get this solved you will know more about the bus than you ever imagined. Why is it we get experience just after we need it?

[0533]

I am sure glad that I did not learn to fly this way. Although I did have a few experiences that were almost the same.

[Coloradobus]

A bad cell in one of the chassis batteries can wreak havoc, where nothing makes sense. Bruce, since you have 24 relays that make your brake lights come on with the jake, pull it and see what happens, also, try pulling the jake brake relay, as well.
I suspect though, as Prevost, its in your toad wiring harness.

that my 2 cents

[0533]

Its worth twice that much at least. Thanks Jim, I will be climbing on this problem in the morning.

You have a Marathon, could you also direct me to the so called Jump Start Relay Solenoid, what does it look like? It is supposed to be above the chassis batteries along the top of the inside Door??? I was going to test this as well.

[Jon Wehrenberg]

Bruce......please disconnect that alternator and chassis battery cable from the isolator and hook them together. If the voltage does not go down with Gen power or shore power working we can start presuming it is an isolator problem on the low votage issue. If the jump start relay was closed the chassis batteries would be seeing house battery current.

[0533]

I have made a list for tomorrow and this test is on top of the list. I plan to do a complete check list of testings.

[Coloradobus]

Bruce, I will have to look in our battery bay in the morning as well., curbside behind the tag. Our chassis batteries are not located where yours are. We have an "H".

[0533]

Good point, Have you ever noticed the Jump Start Relay before?? I am drawing a blank on the location and what the Solenoid looks like

[Coloradobus]

Bruce,

Yesterday , rolled the toll window down, reached in and hit the jump button, resulting its clunking sound somewhere at the backend of the coach. If its in the engine compartment, we can't open the rear hood with the bus inside. Can't pull it out because of a snow pile we are waiting to melt.
Good luck. Have you called Leon at Camp Marathon?

[0533]

Nice low tech way to do this, will follow suit on this one. Marathon thinks the solenoid on the relay is stuck on. I have been tied up and meetings for the past two days plan on going over this afternoon and getting to the bottom of this.

[Jon Wehrenberg]

If the relay is stuck on the chassis batteries and the house batteries should read the same, unless the relay disconnects the chassis batteries from the bus starting system, and switches starting system voltage to the house.

I doubt that but go for it. Two minutes connecting the alternator and chassis terminals will give you a bunch of information.

Got my neck stuck out again.

[0533]

Jon I am now getting ready to head over to the bus and do these test,

I believe that on the isolator there are 3 connections, one is "Main" One is "Alt". and one is "Aux" I get the lower reading off the "Main" which I believe to be the Chassis Battery. It is my plan to disconnect the "Alt" cable and the "main" cable and connect the 2 together. then go through the process of testing and running the Genset or even the shore power I guess. I also plan on turning off the shore, the 12/24 the house and the inverter power before disconnect and connections are made. i will also test the lines before turning any wrenches

[Jon Wehrenberg]

I don't think you need to do any disconnects when you detach the two cables from the isolator if the engine is not running.

The alternator cable should be easily traced to confirm it comes from the alternator and I agree the main sounds like the chassis.

Just as information, as long as none of these contacts a ground there is no hazard associated with what you are doing. Even if you connect the wrong ones together there will be no problem. You may not get the answers you seek but there will be no damage to anything because when the bus engine is running and the inverters are not powered you already know the alternator power on the bus powers both other cables through the isolator, effectively tying all three together.

By connecting the alternator and chassis together, and running the generator or connecting to shore power you have separated the chassis from the house unless the jump start relay is closed. By separating the two systems you should see the chassis charged via the alternator, something apparently not happening now when the house inverters are chargers. If the jump start relay was closed it is my opinion the chassis batteries would be charged via the inverters and would not drop down in voltage.

[gmcbuffalo]

Bruce
Any news on your latest troubleshooting?
GregM

[0533]

I have been traveling on business, as this is my busy season and I have been putting the bus off I am afraid. Had hoped that when I returned the bus would be healed on its own, buses have a way of doing that you know.

Before leaving I went through several tests, changed out a few parts and pieces, but am still planning on heading back to Jax. for a Prevost look see, can't seem to spend enough at Prevost.

I was actually considering bringing in an electrician to take a look around, but canceled the idea as I was not sure what to tell them.

I will be heading down to Fiesta Key on the 23rd., a few POGGERS will be there, if I am still having problems by then maybe one or two will give me some clues, steer me in the right direction.

It does not take much to elude me when dealing with mechanical stuff.

PS> I replaced the Valve in the Steer Bay that controls the Step, it was leaking air fast, it went well, no leaks all went together just fine, but there was a little resistor ??? that ran between the two leads, I was able to move it over to the new connection without too much trouble, except one small problem the step will not slideout, no power, need a new dohicky I guess as the connection worked out fine, "NO LEAKS" half way there, says aired up.

[Jon Wehrenberg]

Prevost will happily keep changing parts as long as you have a line of credit or money in your wallet. (Next time maybe you should ask them if they will take back the parts and credit you for the cost of labor if their parts replacement does not work.)

The key to all this Bruce is diagnosis, and Prevost apparently isn't doing that and you are aiding and abetting them.

[0533]

Actually Prevost is not at fault here, I am. The only thing they did last visit in this regard was to reset my ABS light, nothing else in the electrical troubleshooting process as there was not a big problem.

It has however become more of an issue since I was at Prevost, they did connect a new ground strap on the Alt. a few odds and ends house keeping stuff on the engine, a few upgrades etc, but nothing other than the ground strap and the resetting of the ABS light.

I however changed out the Regulator as I was convinced it was bad, as it was showing high voltage on the chassis batteries when I conducted the test by placing a jumper wire on the Fld and Alt for a few seconds, the Chassis voltage ran up quickly to 32volts output, so I replaced it. I also replaced the EM70A Vanner monitor (crossed my fingers on this one) it sure looks pretty.

I inspected all wires, batteries, leads, you name it, tightened, cleaned, painted (corrosion stuff) everything. It was almost 6pm dark and I did not want to bother my neighbors with the noise of running the bus, went home and flew out of town, am now back plan on checking out my handy work. Do not expect much as I was doing three things at once, voltage, step and Auto Fill, think my solenoid is bad, on the water fill everything else is fine.

It is funny though, that it is either nothing wrong with the bus or there are a few issues, I prefer nothing.

[0533]

I am just finishing up a few details here at Jax Prevost, am up in the air inside Bay #2, the one where you have to leave your wallet at the front desk before entering.

Here is what we found and what was done to address the problem. Let me first say that Wally and Cliff here at Prevost Car really spent the time to actually sort out all aspects of the problem and truly resolve the issues.

Anyway: 0533 is a XL45 1998 shell converted by Marathon, this will create the baseline for discussions moving forward.

Marathon equipped this coaches electrical system as follows: There is 1 270 Amp alternator that goes to a series of Vanner equalizers and on to an Isolator, big blue finned cylinder that separates the alternator from the the house battery bank. Housed inside the Isolator is a solenoid that has 2 leads attached that can be used to jump start the chassis batteries in the event of a chassis battery drain, switch is on the dash. The isolators solenoid is housed inside the sealed housing, bad idea. Costly one as well.

Testing process: If we placed a voltage meter on the Chassis side of the isolator (chassis leads removed) we saw 24.87 volts which was the same as the House battery bank. If we removed the house battery leads from the isolator there was no current passing across to the battery side.

Conclusion was that the isolator had failed, and the internal solenoid was allowing current to pass current across the isolator from the house to the chassis side, not the other direction, we replaced the isolator. No current issues after this was done.

We also disconnected all batteries both house and chassis, tested each with a meter (Snapon meter clip leads and three readouts) that could check the values of the battery beyond its current voltage, discharge and had a meter that once pressed would create a colored scale to check the condition of the lead acid plates etc, not exactly sure here but the results were interesting, had 3 bad chassis batteries and 2 bad house batteries, all of the rest were reading good or very good.

Operation: Replaced all chassis batteries and 2 Lifeline house.

Next we took a look at the regulator to check output as the values were still higher than they should be, 29.2 range.

this where things got a little strange. Wally wanted to see where the battery wires (Prevost) from the Regulator inside the Prevost control box above the engine terminated, as he thought they would end up at the switch for the chassis battery shutoff, they did not, the Prevost wire ended up terminating into a Marathon wire that connected to the 24 volt emergency shut off switch above the door at the curbside engine compartment. In other words the regulator was regulating the house battery bank not the chassis battery bank.

Here is why: It appears that Marathon has designed the so called single alternator setup to supply charge first to the house batteries so that when the house shows a need for a charge the alternator will charge the house bank so that the house batteries can be fully charged while the bus is running down the road without the need for the generator running. In fact if you do run the generator the alternator stops charging completely, in fact the chassis batteries are getting no charge at all to my knowledge (maybe they would as a result of the Vanner equalizer sensing an unbalanced condition, not sure here), anyway it is completely the opposite of how Prevost ties the regulator battery wire to the chassis batteries.

Here is what we think was happening to cause the problems overall: First the regulator output was too high and needed to be cut back, it is now set at 27.9 volts. 2. When the house battery bank was calling for power (2 bad house batteries one really dead) the alternator (which works just fine) starting sending power to the house and at the same time was overcharging the chassis batteries (isolator was not isolating) frying them not a pretty site.

With 3 out of 4 chassis batteries failing or near death I was getting all kinds of strange events going on in the coach, not now, all is fine, no surges, no over voltages, nice solid clean 27.9 volts readings under all loads, no spikes.

I had a chance to change the way the regulator is connected to the house side, could have moved the wire over to the chassis side but did not, will monitor all from now on with a better understanding of how the system works and why.

That is all for now, hope I have been able to explain this so that Marathon owners will be able to use the info.

[Kenneth Brewer]

Thanks for taking the time to explain the problem(s). what was done to solve the problem(s), and the converter based wiring system/philosophy impact. While our coach is by a different converter, it is still instructive to have this info.

Good luck and thanks.

[JIM CHALOUPKA]

Thanks for the update Bruce, I am sorry you had to go through the ordeal of figuring out how your system worked, and in such a troublesome and expensive way.
It would have been nice to have had printed information in your manual as to the principles of your systems method of operation.
It has been said here many times that one only learns by their mistakes. Now I hope we can learn from our experiences, or in this case yours.
Even though our systems may be different, your experience shows that some operations are concealed inside devices and that nothing should be assumed when diagnosing a problem.

JIM:)

[Ray Davis]

So Bruce,

Is it a fair summary that the issue was that (1) the isolator had failed and (2) the regulator was putting out too high a voltage? That caused the fried batteries, which ultimately displayed the issues you saw?

Ray

[0533]

Good morning,

It is a combination of my inexperience with Prevost ownership coupled with the converters desire to create a better mousetrap. The trap is created when the converter changed the regulator battery lead to monitor the house as a primary monitoring source and not the chassis. In a perfect world the Vanner balancing device would keep everything in check, but there was no provision made for an Isolator failure that also housed the jump start solenoid.

The isolator (long blue cylinder with fins) on my bus had 3 lugs and 2 smaller lugs for the jump start, a House lug, an alternator lug, a chassis battery lug and a 2 wire jump start lug for emergency starting. The isolator had the capacity to open the current flow in one direction, from the house side across to the chassis side for a period of seconds while depressing the switch inside the bus. I took a look at a few other buses while at Prevost to check out other installs, and found that some had a simple Solenoid that had both house and chassis at either side separate from any other isolator for this purpose.

My decision after viewing what happened was to replace the isolator with one that could not allow for the jump start feature, in other words it cannot pass (should not) current across from either source. This way I should not be able to fry my chassis batteries in the future. I plan to install at another date simple solenoid and provide a connection from the house and chassis batteries for this purpose, as I retained the 2 wires from the switch inside the bus.

When I do go to Prevost car for service and pay the long dollar, I try and get an education when possible, spend the entire day right next to the mechanic, as his grunt, holding, fetching, and asking questions and taking notes. I even ask in advance if they do not mind if I tag along and stay close at hand for the day. It does add a few minutes to each hour, but I figure that the investment allows me to add Prevost school credits to my education as an apprentice.

Here is one I learned. Did you know that the lugs on all terminals for the batteries, all ground wires to the chassis are required to be torqued to 13 LBS?? I did not and was told that it is the case. At each connection the mechanic would take a razor blade and scrape the metal and make sure the contact was clean on both sides before replacing each wire.

Battery condition: I was always under the impression that if each battery, disconnected from the rest of the bank read lets say 13 volts they were ok. Not so, there is a meter that reads the condition and the ability to maintain a charge and readout if the battery is either dead or on its way. I have been wrong about this for my entire life, no clue.

the final take away from the whole deal is that when you have low voltage you get high amps, and based on our buses and the power demands one should look at the batteries first. The next issue is a short to ground that causes an increase in current, wiring harness for the brakes or bulbs that are shorting out to the chassis.

Finally when driving down the road without the genset operating and all converter power coming from the house batteries the alternator will come on at some point to maintain voltage to the house batteries. I did notice a slight increase in the voltage from the chassis side .2/10's, .5/10's maybe as the ride continued along 4 hours or so. I have decided to knock back the regulator output by .5/10's volt today. I do not want to see the output exceed 28 volts from the chassis side.

The other solution is to add a second alternator, dedicate the big old beast, 270 amp alternator to the house and include a smaller one for the chassis. Not a small operation and not cheap, will stay where I am for now.

[jelmore]

The other solution is to add a second alternator, dedicate the big old beast, 270 amp alternator to the house and include a smaller one for the chassis.

My 12v Liberty is set up with a separate 12v alternator for the house batteries, and that's fed to the inverter/chargers I presume. The big 24v alternator is for the chassis. The two systems aren't connected as far as I know.