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Old 06-28-2020, 05:10 PM   #1
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Brand: Thor Motor Coach
Model: ACE 30.2
State: New York
Posts: 26
THOR #11074
Hot Water Heater Wiring Issues

Getting ready for a trip Tybee Island in July and found that my hot water heater is no longer making hot water. Started with the basics, checked the breaker and the 2 amp fuse on the control module. Checked the thermostat and ECO for continuity and found them to be good. Pulled the connector on the module that supplies 12v to the trigger wire of the 120v relay located on the back-side of the heater and could hear the relay reacting. Hmmm… looks like the 12v control circuit is working.

On to the 120v circuit. Naturally, the back-side of the heater is difficult enough to reach with one hand beneath the galley sink and cabinet and impossible to get at with two hands to do any kind of testing and diagnosis. So, I drained the heater, disconnected the water lines and pulled the heater from the coach.

What I discovered were more examples of poor craftsmanship. In the first photo you’ll notice that the electrical box cover was left hanging. This was due to the fact that they could not fit the birds nest of wire nuts and the relay in that space, which of course also contains the heating element. Above my multi-meter you also see a second taped mass of wire nuts. Those are the 12v wires to the control module on the front-side of the unit. In both cases they used wire nuts with un-tinned stranded wire. The last two photos are before and after of the control module wiring.

In the second photo you’ll see a close-up of the 120v connections. It looked like it had gotten hot. So, I removed the tape and found the neutral had gotten hot enough to melt the wire nut. I dissected the connection and discovered a number of the strands had not made it all the way into the wire nut. In my opinion, this created a two-fold issue. First, the fewer strands that actually made connection where probably carrying more load then intended and second, the loose strands may have been making and breaking contact, both situations contributing to an overheating condition.

Once I corrected those issues, I went on to test the heating element for continuity and found it to be good. However, in taking voltage readings I found that I had 113v going into the relay, but only 105v coming out and going to the heating element. I contacted the manufacturer (Dometic), but they couldn’t provide a good explanation for an 8 volt drop across the relay. So, at this time I am waiting for a new relay to arrive and will post the results once installed.

Happy Travels,

Jerry
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Old 06-28-2020, 05:33 PM   #2
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Brand: Thor Motor Coach
Model: Siesta 24SS
State: California
Posts: 857
THOR #12698
Good thing you were able to find the problem and fix it before your trip.


Paul
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Old 06-29-2020, 01:59 AM   #3
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Brand: Thor Motor Coach
Model: Damon Daybreak
State: New Mexico
Posts: 163
THOR #19133
That looks dangerous. Glad you found it.
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Old 06-29-2020, 02:19 AM   #4
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 5,187
THOR #7035
Unfortunately, one of those things that need to be checked on every new RV from Thor, along with the ATS connections.
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Old 06-29-2020, 01:30 PM   #5
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Brand: Thor Motor Coach
Model: 29h outlaw
State: New Jersey
Posts: 344
THOR #5248
Wire nuts and vibration don’t mix well. That is why I have replaced most of mine with WACO 221 series lever nuts.
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Old 06-29-2020, 01:47 PM   #6
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Brand: Thor Motor Coach
Model: Palazzo 33.3 34'bunkhouse
State: Georgia
Posts: 2,423
THOR #4735
I went thru this recently with our son's 'new' used 07 Rockwood camper, with it's Suburban DSE not working, suddenly, even though for the first week it had worked just fine, with him always plugged in and on the Electric element.

While I used my voltmeter to confirm/check the voltage at the various spots, I found the breaker's output was fine, but nothing at the Element or at the Temp/Limit Switch. The unit's own 'On/Off' switch was hard to press from On to Off and vice versa, but since the unit had been working for a week, I didn't at first suspect that the simple switch was any issue.
But, it was.

While I had power on the circuit, but nothing at the Temp/Limit switch, and therefore nothing at the Element, I started to think that the actual 'on/off' switch on the unit could be the issue, even though I had already ordered a new $10 temp/limit switch thinking that it could be the problem.

When I did some more investigative removal of the physical 'on/off' switch, which is fairly difficult to get to on these units, mostly 'hidden' by the lower Propane lines, I got a sudden 'ARC' and splash of electrical sparks. I had been pulling on the switch with a pair of needle-nose pliers, trying to pull it out of it's mount, in order to get to the wires to be able to put my voltmeter on it. Wow, I knew now that we certainly had POWER to the switch.
After tripping the main Water Heater breaker, I removed the switch body, and for a test, connected the two wires directly together.
After resetting the water heater breaker, and using my voltmeter to check the power to the various parts of the unit, I then found that I not only had power flowing thru the Temp/Limit switch, but then also to the Element - now I know that the physical on/off switch was the issue, for whatever reason.

I thought about replacing the switch with either another just like it, if I could locate one, or even another 'beefier' switch that might be easier to use.

But, in the end, knowing that my son is always plugged in and always has city water, and we'd not be 'winterizing' the camper at any point in the future, I simply tied the two switch wires together with a nose-to-nose connector and called it a day. Done. $0 cost.

(I sent back the $10 temp/limit switch, via amazon, free of charge, too, with a total refund already in my account the same day the UPS store drop-off scanned it)
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Old 06-29-2020, 02:01 PM   #7
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Brand: Thor Motor Coach
Model: ACE 30.2
State: New York
Posts: 26
THOR #11074
Thanks for the suggestion! I think I'll try the Wago connectors.

Jerry
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Old 06-29-2020, 02:07 PM   #8
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Brand: Thor Motor Coach
Model: ACE 30.2
State: New York
Posts: 26
THOR #11074
Very interesting Turner.

Thanks,

Jerry
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Old 07-02-2020, 02:44 PM   #9
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Brand: Thor Motor Coach
Model: ACE 30.2
State: New York
Posts: 26
THOR #11074
Installed the new relay and replaced the wire nuts with Wago 221 lever nuts. Happy to report that I have hot water again and peace of mind knowing that the Wago nuts are in place. Thanks to everyone who read and contributed to this thread.

Happy Travels,

Jerry
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