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Release Version 6/12/13

Notes on Roadtrek Electrical Simulator

Disclaimer:

Use at your own risk. This simulator and these notes are not a substitute for professional

advice. Damage to your RV could occur if you do not follow the instructions provided by

Roadtrek. As an independent owner, the author developed the simulator and this

document to help answer questions posed by other owners.

The information provided here is offered, "as is" with no implied warranty as to the

accuracy or applicability to any of the Roadtrek vehicles and is intended for educational

purposes only.

Working on the electrical system in a motor home entails risks

even with the low voltage wiring. The risks include death,

serious injury and property damage. The AC line voltages can

kill by inducing cardiac ventricular fibrillation. Lead Acid

batteries store tremendous energy and can cause thermal and

acid burns. Batteries produce hydrogen gas which can explode.

The risk of fire must also be considered with the presence of

solid, liquid and gaseous combustible materials. The user must

take full responsibility and assess if he or she is qualified to use

this information.

Background:

The electrical system in your “mobile self contained living unit” is surprisingly complex.

There are multiple energy sources and both high and low voltage wiring. It’s no wonder

lots of folks are confused!

It’s my hope that this effort will enlighten both owners and professionals. I know that I’ve

been enlightened! Please let me know what you think and pass on your experiences.

john@pochiro.com

When I first set out to build this simulator, I along with many others thought incorrectly

that all of these machines worked about the same way with only minor differences. Oh

how wrong I was!

Summary of content (21 pages)

PAGE 1
Release Version 6/12/13 Notes on Roadtrek Electrical Simulator Disclaimer: Use at your own risk. This simulator and these notes are not a substitute for professional advice. Damage to your RV could occur if you do not follow the instructions provided by Roadtrek. As an independent owner, the author developed the simulator and this document to help answer questions posed by other owners.
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Identifying What You Have: Troubleshooting a complex system with an incorrect picture of what you have is a recipe for frustration. An accurate description of the system as built is critical to resolving any problem you might have. Someone may tell you that this is what you need to do and it may not apply at all to your situation. So be sure you know what you have before you start. There are four major configurations which I believe cover most of the Roadtrek’s in use today.
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A battery separator looks like this: On the Sprinters I’ve looked at, the separator is located on the firewall on the driver side of the engine compartment and is clearly visible when you open the hood. I don’t know where it’s located on other vehicles. The next question addresses the connection of the converter/charger to the battery. Some of the schematics do not show the correct connection.
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first four options allow you to select based on the above questions. The other options attempt to answer the questions for you based on the model and year. In your RV, some of the buttons are “momentary” which means that mechanically they don’t stay in the same position when activated. The battery disconnect switch has two momentary positions “ON” and “OFF.” Note that if you hold either the “ON” or “OFF” button down too long, you will get a warning about overheating the coil.
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condition function. When you push and hold the test button, the display will show the battery condition as well as the levels for the LP gas, fresh water and holding tanks. The battery condition lights display the current battery voltage. This may or may not be representative of the battery condition. The “C” light will be on if the voltage is above about 12.7 volts, the “G” light comes on at about 12 volts, the “F” light comes on at about 11.3 volts. The “L” light will come on with less than 5 volts.
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“Separator equipped” vehicles will have changes, but will operate very similar to unmodified vehicles. Vehicle Battery The vehicle battery is a standard automotive type and is used to "start" the vehicle and operate accessories when the engine is not running. This type of battery is not designed to be "deep cycled," but rather is intended to deliver large amounts of current to the starter for short durations.
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time not allow a light or some other load in the RV to drain the vehicle battery. It does this by allowing current to flow from the “A” terminal to either the “B1” or “B2” terminals, but not in reverse. This is accomplished, with some high current diodes. Current can flow from the alternator to both batteries, but current cannot flow from the vehicle battery to loads in the RV. The same is true in reverse, should you leave the vehicle headlights on, the RV battery will not get drained.
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Interestingly, the battery separator consumes a significant amount of power when active. The case will become noticeably warm in operation. This is not a problem since when active; you have a source of power other than the batteries. Automatic Resetting Circuit Breakers In the diagram there are three components labeled "CB" with either 50A or 30A labels. These devices are circuit breakers which will open the circuit should there be more than the rated current flow in the circuit.
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condition of the RV battery. Note that if the RV battery is extremely low, you may demand more current than the circuit breakers will allow during the initial charging. For the best battery life, one should never discharge the batteries completely. Automatic Transfer Switch The generator AC output connects to the RV 120 volt electrical system via an electrically operated switch.
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If shore power is connected with the battery disconnected, the Converter will supply power and the low voltage loads will work if you have the direct connection configuration. Note that the converter may be unstable and the lights may flicker due to the “no battery connected condition.” You should not operate the system in this way.
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measured the idle current demand for more recent GM vehicles is about 5 times that amount or about 60 milliamps. The idle time possible has been reduced to about a week. GM seems to think this does not matter since most of these vans are in commercial service and don’t sit idle. Roadtrek addressed the problem of the vehicle battery going dead while parked by replacing the isolator with a battery separator.
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service manual which can be found on the Onan website has a troubleshooting guide which is very helpful. I learned recently that Onan has stopped using the oil level sensor on more recent models due to the inability to get a reliable unit. You can tell if the engine “fires” when holding the start button down. If it fires then the oil level sensor is not at fault. The generator won’t start The fuel pickup in the gas tank is set high to keep you from running your vehicle tank completely empty.
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After stopping for a time with the refrigerator on DC, the vehicle battery has run down. The refrigerator when running on DC requires a lot of current. This mode of operation is really only intended when you are traveling and can’t run it on propane. With a single battery, the refrigerator can run the RV battery down in an hour or less. The isolator or separator should protect the vehicle battery from discharge if the refrigerator is left on. If this happens, the system is not operating correctly.
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Everything is great until I stop and hook up. After awhile the lights go dim. The only way to get them back is to start the engine. When you are connected into shore power, you should be running off the converter / charger and the battery should be charging. The monitor panel should show “C.” If the converter charger is not operating, you are running off the RV battery even though you are plugged in. First, make sure you have AC power. Check the microwave display.
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the output of a typical 100 watt light bulb. This is of course the reason many rigs have two batteries, but that only doubles the low starting number. I can plug in and the lights work, but it won’t work on battery, I think the battery disconnect is bad. It could be a bad disconnect, but you need to check a few things first. When you operate the switch, you should hear a “clunk” sound from the disconnect. If it does not make any noise, then be sure it’s getting power.
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read a higher than normal voltage until the electrolyte reaches equilibrium. The same is true for a battery, which has been discharging at a heavy rate, when your remove the heavy load, the voltage will be “lower” than normal and return to a value based on its state of charge after a period of time. Don’t jump to conclusions with limited information. The warning light usually indicates that the voltage at the battery is too low and the battery is not charging.
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has failed “open” it will read much higher. In the case of an open diode between the A terminal and the vehicle battery the voltage may be 20 volts or more with the engine at idle. Measure the house battery voltage at the isolator with the engine running, it should also be about 1 volt less than the alternator output. If it’s much less, (Battery voltage more than 1 volt less than the alternator output) then that side of the isolator is bad and it’s not charging the battery.
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not have enough voltage to switch on the diode and you may think it’s open. Switch the meter leads and you should see it conduct one way and not the other. A-B1 should conduct with A more positive and B1. A-B2 should behave the same way. E-A should conduct when E is more positive than A. B1-B2 should not conduct either way. You can use a battery operated test light to check the diodes as well.
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General Troubleshooting Tips Systems operating in failure mode can behave in very strange ways! The situation is not “normal” and the goal is to figure out why. It’s important to examine the conditions and think about the problem before blindly diving in. What combination or conditions could create the condition I am observing? Digital voltmeters DVM are wonderful tools, but they can mislead. A voltmeter draws a tiny amount of power from a circuit.
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Replacing an expensive part only to have it fail immediately because of another problem is quite annoying! So think, check and verify. Walking away from the problem for a few minutes or hours can work wonders. Closing Comments: I have spent more time on this than I should, but it’s like working a puzzle, its fun, but there are other chores I need to be addressing. I will be happy to add features as time permits and I will fix any bugs promptly if they are brought to my attention.
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configuration. Added a note to the screen about voltages to avoid confusion about absolute values. 4/18/10 Major revisions to the notes and corrected the simulator to reflect the four configurations described. Added battery monitor panel display function. 4/5/10 Fixed a bug where the converter trace would show red with no voltage. 4/1/10 Changes added to provide for direct connection of converter/charger/inverter to the battery.