Another Electrical Mystery


by Ken Freund
May 31, 2016
Filed under RV Tech Q&A



I own a 2010 Freedom Elite made by Thor. Everything electrically worked fine until a recent trip. When not connected to shorepower, the inside lights don’t work, nor does the refrigerator — anything not off the starting battery is inoperative. However, when parked and plugged in, or with the generator running, it all works. After I noticed this, I replaced the coach batteries, as they would not hold a charge to start the generator. The work was done at an Interstate battery dealer that has done other motorhomes. I checked, and all cables on those batteries were tight. I have checked all circuit breakers, fuses and obvious things I know. I have flicked the battery disconnect switch by the door on/off with no change. Nothing works; what do you think it is? Can converters cause issues like this?

Gary Warden | Kingston, Tennessee


CP-InfoYou haven’t made it clear if only the 12-volt DC circuits are dead without shorepower or the genset running, but from your limited description of what doesn’t work, I’m going to assume that the 120-volt AC system is working normally and that the problem is confined to the 12-volt DC system. You also didn’t say how long ago the batteries were replaced, or if that got things working, at least temporarily. Since you get 12-volt DC power when you’re on shorepower and genset power, the transfer switch and power converter are working. So basically, the only other source of 12-volt DC power is from the batteries.

So, you need to start at the batteries, with a voltage test to see if they’ve gone dead. They should have about 12.6 volts when fully charged. If they are charged, then you need to follow the cables from the batteries to the fuse panel and see if you have power there (which is doubtful, except when the shorepower and the converter, or the genset and converter, are powering things). It’s likely power is not getting through the protective circuit breaker or the battery disconnect switch, either because it is faulty, or not getting switched on. A jumper cable could temporarily bypass the relay, but if you aren’t sure what you’re doing, have an auto electrician do it.

Frosty Fridge

We have a 2012 Itasca Reyo motorhome. The refrigerator ices up with frost after about 10 days of use. Is there a product I can put in the refrigerator to help with this problem, or should I buy a new refrigerator for longer trips?
Thomas McCall | Smithsburg, Maryland


The refrigerator you have is a Dometic RML8555 three-way model, which realistically is as good as you’re going to get in the motorhome world (without replacing it with a residential unit). The first thing to ask is, “Where’s the moisture coming from?” Some users are in and out of the refrigerator constantly, and the complaint that usually parallels a frosty interior is that the refrigerator doesn’t cool correctly. Many owners have an unrealistic expectation that these absorption refrigerators should perform similarly to a compressor-powered residential unit, which is part of the learning curve. You didn’t mention if you have had other motorhomes with absorption refrigerators. Additionally, with the small cubic feet of interior space inside a motorhome compared to a home, ambient moisture is normally a bigger issue. Often owners cook, shower and hang wet clothes in their motorhomes and many do so without opening roof vents or windows, and it lends to a high humidity level inside the coach and condensation on interior surfaces when it’s cooler. It’s reasonable to expect each time the refrigerator door gets opened, a new charge of humid air is introduced and the frost begins to build up. This is considered normal, but behavior can be modified to improve the time between defrosting efforts.

Another possibility is a mechanical issue that could be a simple door seal that’s constantly leaking air. I’d have a good look at that door seal first. Ensure the seal isn’t distorted or twisted, nor has any high or low points and no gaps exist. I recommend a tried-and-true procedure; use a strip of paper (a dollar bill for example) and shut the door on the paper and do a series of pull tests (you should feel drag). Additionally, the frost doesn’t always build up at the source of an air leak, so inspect for other leaks in the cabinet.

12-Volt DC System Failure

We have a 2008 CT Coachworks Siena motorhome that we bought used. Earlier this year we had an electrical blackout at our house and decided to sleep in the motorhome. We ran the genset for an hour or so, shut it down and went to bed. Next morning nothing worked and the genset wouldn’t start. I took both deep-cycle batteries to have them charged. After six hours I went to pick them up, and was advised one would only hold a 50 percent charge; the other wouldn’t charge at all. I bought two new Interstate deep-cycle batteries. At first, the inverter had fault code 36 and the charger had fault code 71. It’s an Onan 2000. The remote battery disconnect doesn’t work. With shorepower connected, the inverter blinks and the charger still faults to 71. I took it to two RV service centers and neither one could figure out the problem. The engine and genset work, but the 12-volt DC system just doesn’t work. I changed the fuse to the inverter/charger but that didn’t help.
Frank Tavares | Portola, California


Before you can get the system working, you need to have a battery bank that’s charged and working. A basic approach is to start at the batteries and measure voltage there, then at the disconnect relays, and then on to the power panel and fuse box. From your description, it sounds like you may have more than one problem.
I called CT Coachworks and the company is willing to help you even if you are not the original owner. CT is located in Riverside, California, phone number 951-343-8787. The Onan model 2000 is discontinued, so if it has failed, unless you can find a good used one for a reasonable price, your best option will probably be to replace it.


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One Response to “Another Electrical Mystery”

  1. Mike Roberts on July 21st, 2016 8:53 pm

    Reading some of the issues trouble 12v sysrems.
    Some consumers may be confused about what a inverter does and what a converter does.
    so for those of you standing there trying to figure out what does what and your owners manuals have run away from home. Never to be seen again.
    I will make it simple for you.
    a inverter takes 12vdc and turns it into 120acv (house current)

    A converter on the other hand operates like a battery charger.
    it uses 120acv and converts it to 12vdc to be used to operate 12v devices and charge “house batteries”
    Hope that cleared things up
    if you are having 12 volt issues the inverter isMOST LIKELY NOT YOU PROBLEM
    look for connection problems, fusess, switching problems such as relays.
    ground connections have been a huge culprit. And can cause bazzar symptoms. If your problem is bazzar starrt with making sure ALL GROUND connections are good. AND THERE CAN BE MORE THAN ONE GROUND IN 12V SYSTEM.


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