Sneaky Circuitry
I am working on an electrical problem in a friend’s 2003 Holiday Rambler Traveler 26RB2. On the wall by the outside door is a push-button switch, whose purpose is to disconnect the coach battery from everything but the refrigerator and the inverter. The switch operates a large contactor in the driver’s-side storage area. One push opens the contactor; another push and the contactor closes. If there are any lights on when the switch is operated, they are supposed to go out.
That is the way it used to work. Now, however, it doesn’t “” at least not always or completely.
When I was first shown the problem, the lights went sort of dim. When the switch was pushed again, the lights would come back to their normal brightness. Push the switch again and they would go dim. I measured the voltage on the 12-volt-DC bus in the fuse box, and it registered 12 to 13 volts with the switch on, and 9 to 10 volts with the switch off.
So, I took apart various sections of the wiring and proceeded to check the batteries and the fuses. If the switch was left off long enough and more lights were turned on to accelerate the process, the lights would get dimmer. At some point the fluorescent tubes would blink and go out.
It looked to me as though there were a battery hidden in the coach somewhere that was back-feeding the system when the main coach battery was off. Eventually, I found fuse #17, which is labeled “Power Toilet” and connects to a blue wire, in the DC fuse box. With that fuse removed, there are 12 volts on the downstream side of the fuse connector. When the fuse is removed, the motorhome’s battery disconnect switch functions normally: switch off, lights out; switch on, lights on.
The blue wire has 12 volts on it when the fuse is not present. When the fuse is present and the battery switch is off, the 12 volts is back-feeding the panel.
My question is, where does this blue wire, marked “Power Toilet,” go? There is a blue wire that terminates under the bathroom wash basin that has no voltage on it regardless of the switch position or whether the fuse is in or out.
I called Holiday Rambler tech support and was told to leave the fuse out. So I guess we will leave the fuse out and see what goes dead.
I must add that this phantom battery is likely not the chassis battery. When the phantom voltage is down to 6 volts and the lights are dim, the chassis battery cranks and starts the motor just fine. With the motor running, the phantom’s voltage does not change. Any ideas?
A.J. Oxton, F85558
Tonopah, Arizona
A diode on that blue wire should work to stop the back-feeding problem. However, something is supplying the voltage, and the source of that electricity really should be found. A tracer generator could be put on the blue wire to try to determine where the voltage is originating. There could be a staple or screw in the line somewhere. I agree with the Holiday Rambler service technician’s suggestion to leave the fuse out until the source of the problem can be found.
Generator Question
I own a 2007 Fleetwood Southwind motorhome equipped with an Onan 5500 Marquis Gold generator. My generator recently had a complete maintenance service. When started at home, it runs smoothly for about 10 minutes, but then it stops as though I had manually turned it off. When it stops, there is no choking or coughing “” it just quits running. After a wait period, it will start and run again for about 10 minutes before shutting down. I took the motorhome back to the mechanic and, predictably, the generator ran for five hours. Once I got it back home it started the run-and-stop routine again. Is it possible that a bad fuel pump or varnish in the generator from bad gas coming from the motorhome could be causing this shutdown problem?
Wayne Welsh, F387461
Miami, Florida
Your letter doesn’t mention whether the 5500 model generator you have is equipped with fuel injection or a carburetor, so I’ll cover both possibilities.
Assuming that your motorhome is gasoline-powered and a gasoline filter is installed before the fuel line’s connection to the inlet on the generator, check for the possibility of fuel varnishing, which could restrict the flow of gasoline through the filter and subsequently into the generator’s fuel injector system. If a gasoline pre-filter for your generator does not exist, it may be necessary for a generator technician to inspect the fuel injector.
If the generator is equipped with a carburetor, varnishing also could occur if fuel is left in the carburetor and the unit is not used for a long period of time. This could occur even when the gasoline in the motorhome’s tank is fine. If the generator sat unused for a lengthy period of time “” even before purchase “” varnish is a real possibility.
Other causes could be a weak fuel pump, a clogged generator fuel filter, a cracked or pinched fuel line, or a bad pickup tube in the fuel tank.
Coach Fire
Earlier this year my motorhome caught fire and was completely destroyed. The fire marshal’s office said they are pretty sure the fire was caused by the cooling fan in the convertor. They said that if the fan fails, it can cause the transformer to overheat. This can cause the diode to fail, which will cause the voltage to increase to the batteries. I thought you may want to research this and let members know.
Bruce Howard
Thornville, Ohio
I was concerned after reading the above letter, so I contacted Gary Baxter at Magnum Energy. Here are his thoughts:
“It’s hard to say what happened here, but we see a lot of reports of fires that point to convertors and inverters, yet after investigations, the causes are usually found to be something else, such as loose or bad wiring, etc.
“The convertor should be UL listed. Depending on the listing, most power electronics are required to have a safety shutdown built into the device. UL testing usually also includes catastrophic failure testing in which, basically, you make the device fail to see if it catches fire, shuts down, etc. You can’t really test every scenario, but testing usually includes a couple of failure tests. If there is fire, which can happen in the failure testing, it is supposed to be contained inside the box so the adjacent area is not affected.
“I don’t know what listing or testing the convertor had on it, but any power electronics device could fail for a number of reasons.”
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