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[jihealy]

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