Ground fault interruptions
In the January 2008 “House Calls” column, Jeff Hayes wrote about his new RV tripping the ground-fault circuit interrupter (GFCI) breakers at his house and at campgrounds as soon as he plugs in the shore power line (“Trippy GFCI,” page 28). I have a motorhome that did exactly the same thing. It has 50-amp service; the campground had 30 amps, and I used a standard adapter. While using the generator, or with a non-GFCI circuit, everything seemed fine. I tested the outlets as you described, and they all checked out okay. I took it to the dealer and everything checked out. But as soon as I plugged into a GFCI circuit, the transfer switch would engage, and then the campground GFCI breaker would trip.
I eventually discovered that there was a short between the ground and the neutral in the wires going from the RV’s breaker box to the front roof air conditioner. This was due to a staple that was inadvertently placed through the cable when the motorhome was being built. If it had shorted out the hot lead, the problem would have been picked up at the factory. The ground and neutral are both 120 volts with respect to the hot, but they are separate leads and should not be shorted. So, if you just check the wires with a voltmeter, you can be fooled. Everything seems to work fine, but there actually is a ground fault; hence the campground breaker trips.
So, how did I discover the problem? That’s a much longer story that required quite a bit trial and error. If you are having problems and would like to do your own investigation, here are a few safety rules:
1. Always unplug the shore power before fooling around with the wires. If you have an inverter, disconnect the house battery as well.
2. Repeat Rule #1.
3. After following the above rules, always check the wires with a multimeter anyway to make sure they are not powered.
4. Before disconnecting any wires, label everything. Use diagrams liberally.
I started by disconnecting the leads going into the transfer switch to make sure there wasn’t a problem going into the switch. Then I plugged the RV back into shore power, and the GFCI breaker did not trip. So I unplugged, hooked the transfer switch back up, and disconnected the main leads going into the RV main breaker box. I plugged it back into shore power and had no problem.
Now I knew that the difficulty was after the main breakers. So I unplugged, hooked the mains back up, and completely disconnected every circuit coming off the panel. This is where the labels came in very handy. I added the circuits back one at a time, each time unplugging, adding a circuit, plugging back in, checking the GFCI breaker, unplugging, etc. Ultimately, I found that every time I added the front roof air conditioner circuit, the GFCI breaker tripped, even though the roof air unit was off.
I disconnected the 120-volt wires from the roof air conditioner, and still the GFCI breaker tripped. Now I knew the problem was somewhere in that wire, so I isolated it from the box and from the roof air unit, and tested the leads for a short. I found that there was no resistance between the ground and neutral leads! So I left the wires disconnected, capped the ends, and took the motorhome back to the dealer. They eventually had to pull the refrigerator to rewire the unit, and that’s when they found a staple in the original wire. I haven’t had an electrical problem since.
Stephen Bodney, F569D
Corydon, Indiana
Thank you, Stephen, and let me add that RV owners who don’t feel perfectly comfortable working with potentially hot 120-volt wiring should have a certified, experienced technician do this testing for them.
I had the same issue with a Bounder and found that the problem was being caused by the convertor. On some units, convertor manufacturers needed to ground the electronics in the unit to eliminate electronic noise. This caused a small amount of current to feed back into the electric cord and trip the GFCI receptacle. If this is the problem that Jeff is having, he can test for it by unplugging the convertor and then plugging into a GFCI-protected circuit. Another method is to plug in his ground cord in such a way that the ground prong of the plug enters the receptacle first (this requires inserting the plug at an angle). I hope this helps.
Ed Burrows, F192818
Agoura Hills, California
On units that I have investigated “” I am not a professional technician “” the problem has always been the factory wiring. Somewhere in the coach the coach builder tied neutral to ground. In most cases it was at the inverter, and one time it involved the air conditioner. But it always turned out to be a factory installation problem.
According to the National Electrical Code (NEC), the ground shall not be tied to neutral except at the source, which is the power pole. An easy way to check this is to take an ohmmeter and measure the resistance of ground to neutral. You should see an open circuit. The coach in question must have only had a 30-amp cord, as I have never seen (they do exist) a GFI on a 50-amp circuit.
Gary Carter, F58342
Minnetonka, Minnesota
Odor begone
I own a 2004 gas-powered National RV Dolphin II, very similar to the 2000 Tropi-Cal mentioned in the “Objectionable Odor” letter in the February 2008 “Tech Talk” column (page 24). I had a very similar experience with a foul odor. Plus, it kept setting off the carbon monoxide alarm. I checked everything but could not find the source. Then I opened the battery enclosure. The coach’s chassis battery was boiling and releasing the foul odor. I corrected this problem, and no more odors. This could be the cause of the problem in the Tropi-Cal.
Keith French, F348666
San Diego, California
The odor that Mr. French experienced could well have been hydrogen gas, a highly combustible gas caused by the tremendous internal heat generated when a battery is overcharged. This is quite common in open-cell lead antimony-type storage batteries that require the fluid inside the battery to be periodically inspected and topped off. This is not a problem with lead calcium sealed batteries that include just a couple of small vents, lessening the chance of gas release and buildup, and which operate at a far lower temperature, greatly reducing the chance of explosion.
New radiator needed
I have a 1984 27-foot Pace Arrow with a 454-cid Chevrolet engine, and it needs a new radiator. Will a radiator from a P-30 Chevrolet chassis work?
Dale Link
Cambridge, Ohio
The radiator that came with the P-30 chassis under your Pace Arrow motorhome may have a higher-efficiency transmission oil cooler in the outlet radiator tank than a radiator on a standard P-30 chassis. If you are in a position to compare the two radiators you refer to, look at them side by side and compare every dimension, every visible detail, etc. One major issue to watch for is which side of the radiator (right or left) the transmission oil lines are on, as they change depending on the model year. Have you considered having the original radiator recored?
Connection selection
I was just reading the “Satellite Internet” letter in the February 2008 “Tech Talk” column (page 22). You stated folks could purchase a wireless card or modem that could be connected to a laptop or personal computer. I think you should include the information that if they purchase a USB air-card, in many cases it has a connection for an exterior antenna. This can be an important feature for those of us who do not necessarily stay in city areas. The exterior antenna has been a great asset for us.
Eloise Cunningham, F156798
FMCA Mail Forwarding
Core meltdown
How do I remove and replace the heater core on my 1994 type A Winnebago motorhome? It’s leaking and I need to replace it.
Richard Decker
Billings, Montana
Are you experiencing a puddle on the floor in front of the copilot seating area? Or is there moisture on the inside windshield when on defog/defrost? If so, here’s a little tip. Check whether the gear-type hose clamps (if applicable to your motorhome) that secure the heater hose(s) to the heater core connector pipes are tight. Through years of use, these connections experience multiple expansions/contractions with each heat-up/cool-down usage cycle. If the clamps become too loose, leaking can occur. Be careful not to over-torque if geared clamps are used.
Typically, the heater core on a Winnebago type A motorhome may be under the dash, possibly in front of the copilot chair. If that’s the case, then I would unbolt the chair, move it aside (to provide visibility and inspection room), and study the “box” that the heater core may be mounted in. The exact procedure to remove and replace the heater core may be explained in the “shop manual” for your particular model coach.
Bell crank replacement
I have a 1987 Mallard on a Chevy P-30 chassis. When replacing the bell crank on the driver’s side with the SuperSteer Bell Crank, is it necessary/advisable to replace the other one?
George Blum, F172365
Madison, Wisconsin
It is not necessary but very strongly recommended.
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