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Old 12-19-2019, 02:37 PM   #1
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Tale of Whoah (Suburban water heater repair report)

I've got a Suburban SW10DE water heater in my new-to-me 40' bus. It's the kind that does propane and 110ac. I didn't know anything about these when I bought the rig, but as it needs most of its subsystems overhauled, I figured it would be just another thing to learn about as I went along. I was right. When I got around to sorting out why the propane worked but the 110ac did not, I got a fair education in RV water heaters. Follow along . . .

The water heater has a short (9"), 1440w "High watt density" electric element. The element has two wires on it. A black one comes from a thermostats/high limit switch. Working backwards, the thermostats is connected to a small, 15a rocker switch that lives on the tank housing in the lower left quadrant of the hatch.

From there (working backwards) the wires run to a junction box on the outside of the tank insulation, easily accessible on my rig through the basement hatches. The chassis wiring connects to a more traditional looking AC switch on the control panel way up front above the stairwell. That switch is fed by the breaker panel (breaker 4, left side). The switch is a two-pot footprint, but the second switch location is filled with an indicator light.

That was the setup, in case a reader can use a description of the layout. Now the event:

When I bought the bus (2001 40DP Mountainaire) for $9500, I knew I was going to pay the difference between the purchase price and a functional home in repairs, overhauls, and upgrades. That's how it works -- pay the big bucks up front and get something nice, or buy an unloved one and pay the big bucks over time making it yours. Among the nonworking "appliances and accessories" (per the owner's guide tabs) was the a/c side of the water heater. The propane side worked, but it's expensive and problematic to get more propane when the bus is not drivable. They won't come to me, and I can't manage more weight than a bbq tank. So I felt the need to fix the electric side.

I assumed the water heater hadn't been serviced for several owners, and that it had probably been electrified with no water in the tank by someone just pushing buttons during sales attempts. So I ordered in a new anode and a 1500w element. That and a good flush should be an adequate tank overhaul.

After cleaning the tank, sucking the rust out of the fire tunnel for the propane side, and installing the new element and anode, I flipped the breaker. . . . and nothing. Boo! Hiss!

I did some reading on IRV2. They mentioned that little rocker switch on the tank itself. I found it. It was on. It would not go off. It was melted to a lump.

I pulled it and ordered another. In the meantime I found a 15a toggle switch in my stash and installed it loosely, on account of it didn't fit the hole. Incidentally, neither did the replacement switch. If you're reading because you have a bad switch, be careful. They use two sizes of these mini-rockers on a 2001 40DP Mountainnaire, and this is the other size. The one you want is larger, has two ANGLED spade connectors on the back, and clearly has room for a third post (but the post is not present).

Ok -- turned the breaker back on with the switch replaced and still nothing. I got the multimeter out. I could not see power at the element. Back to IRV2 for more reading. Incidentally, that Biscuit guy knows his stuff!

I could not find a live link to wiring diagrams, but I was able to sketch out the map by descriptions in the topics. I went next to the switch above the stairwell. The light was on. It went off when I toggled the switch and back on when moved. But still no joy.

But did I feel a little gritch in the switch as I gave it that twitch? I pulled the faceplate. Pieces of shattered Bakelite rained down the stairwell. All the innards were exposed. "Well, there's the problem right there," I said to myself.

A quick trip to the hardware store (it's a common switch), and the switch was replaced. Rinse and repeat the test -- breaker on, switches on, no joy. I had power through the switch but none at the second switch.

I read some more -- circuit board controller, junction box, thermostats/high limit . . . . I was getting into the less charted territories, but I was doubling my understanding of the water heater. I probed the thermostats -- no power in or out. It seemed clear to me (finally) that my problem was unusual -- like a broken wire in the run through the chassis?

I did some more reading. I couldn't find anything directly relevant, so I decided to get in with it. I climbed into the basement bay adjacent to the water heater and examined the wiring for chew marks and damage -- found none as far as I could see. I opened the junction box and found both the black and white wires completely burned away from the wire nuts, and insulation melted an inch or so down the length of the burned ends. Suddenly I knew how my Prosine 2000 inverter had perished . . . .

I trimmed back the wires till the copper looked right and renutted them together. An hour later I was measuring 125ļ at the tap.

So this was a case where almost EVERYTHING was bad -- anode, element, two switches, and the wire. The only thing I did not need to replace was the thermostats, and I might do that to get 140ļ water.
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Old 12-19-2019, 02:56 PM   #2
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Really common situation. The element shorts out and takes everything else out. The limit switch packs are also very prone to burn out. 20 dollars at most any RV parts store will get you new ones.
Went thru this whole mess myself plus replacing the wiring between the toggle switch and the limit switch pack, as that is also a common failure point. Just a word of caution, all the wiring needs to be high temp wire. Otherwise it will get cooked again after a few heat cycles.
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Old 12-19-2019, 03:21 PM   #3
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Yes, the wire quality is important. I'm using tinned, immersion grade, high-temp marine wire (ancor) whenever I replace any -- even my 4/0 battery cables. I buy the stuff by the spool whenever I need a different color or grade. The lighter gauges come in single conductor and also a "romex-looking" 2+ground. The stuff is not cheap, but it's as good as it gets. One way around the expense is to buy a couple of colors in your common gauges and use shrink tubing to "color label" them.

One added advantage is that while modern common automotive wire insulation is now made from corn and soy, marine grade is not. Think vermin attractant . . . .
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Old 12-19-2019, 04:29 PM   #4
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Suburban OEM wiring for 120VAC & for the 12VDC







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Old 12-21-2019, 12:29 PM   #5
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Glad to see you're back in the saddle Old-Biscuit!
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Old 12-21-2019, 12:30 PM   #6
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Quote:
Originally Posted by Old-Biscuit View Post
Suburban OEM wiring for 120VAC & for the 12VDC







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Old 12-21-2019, 12:40 PM   #7
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Ahha, the old Suburban water tank overhaul project.
We've all been there. The good news is they're a pretty good tank and recover nicely on gas/electric simultaneously. Parts are readily available and fairly inexpensive....except the dreaded circuit board failures I've read about.
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Old 12-21-2019, 01:13 PM   #8
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Wire nuts are fine.....so long as you twist the wires together with pliers before you install the nut. I can number how many residential circuits Iíve repaired that the electrician held two wires together and twisted the nut on , never mechanically joining the wires.
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Old 12-21-2019, 01:31 PM   #9
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I haven't seen many melted or come-undone wire nuts in my life, but I don't do ac wiring for a living. With that said, I've seen at least as many on this bus as everywhere else combined. The melted nuts and attendant havoc wreaked in my Xantrex prosine had me puzzled, since there was this humongous inline fuse between the power source and the melted nuts. But when I found the ones in the j-box I think the xantrex issue became clear.

As you suggest, getting a good mechanical twist on the wire ends is essential to them locking up in the nut. That's tougher to do when you're dealing with more than 2 wires in the nut, different gauges, or if you're joining single conductor to multistrand. My RV does all these things, in a mediocre manner. The rig is 18 years old and multi-owner, so there's no blaming Newmar. Twisting wire nuts isn't an art, but it is a craft. Some people just don't have the talent.

Inside my j-box the inbound black wire (single conductor) was cut back less than 1/2". I could see the tool marks on the burnt end. There was no visible twist effect to it -- it had never engaged in the nut. The loose connection caused heat. The heat melted the nut. The loose black wire started whacking the grounded j-box and eventually found its way inside the WHITE wire's nut. That's when everything melted down.

My strategy going forward is to inspect each nutted circuit as I find it. I've got lots of fresh nuts and a good wire stripper. I Already found the rear slide motor wires suspect and dealt with them.
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