Water Heater Switch Malfunction

[sourdough]

I have an issue that I've not resolved yet (haven't really looked) but thought I would throw it out to 1) post the situation and resolution for anyone to glean info from and 2) possibly learn something that might save me some troubleshooting.

MHC 331RL bought in mid March. Been on 1 trip for 3 months and no issues. On this trip, 14 days in, woke up to no hot water the other morning. I always use the LP/electric for a shower and turn off the LP when done (I did forget that the day prior).

Quick check and no blow/tripped fuses/breakers. Pulled the cover off the heater and everything looked....new. It is a Suburban 12 gal. heater so it has the little on/off switch down in the corner. Pushed it for grins....froze and wouldn't budge. Turned all power off to it and checked continuity through element, reset switches etc. and all was good. Pulled the switch and it the connectors were melted and burned - switch was open (would not close loop). Pulling the wires I noticed I could not separate the 1 black wires for each side of the switch so pulled on them pretty hard....they had melted together with bare metal showing through the insulation. Hmmm.

I will run this out tomorrow but the twist that got me thinking was the bonded wire in front of the switch that would close the circuit. With that connection the circuit should have been "made" and the element turned on just as if the switch was on seems to me.

I figured a bad switch but the more I thought about it I'm wondering where the heat came from, no blown breaker, no electric heat to water heater and good element?? We have been so busy trying to get ready for Thanksgiving and DD's surgery I've let it get by on LP for the last 2 days but now DW is at DD's house and I'm alone so may get some time to check it out. Anyway, checking for any thoughts that might shorten the process; a day doesn't go by that someone doesn't call and need something so hope to zip it up quick (the switch is replaced).

[LHaven]

Two problems, maybe? The short at the switch wasn't a cause, but a side effect of a wonky shorted element?

[chuckster57]

Last one I dealt with had a bad wire from the switch to the thermostat.

[sourdough]

Thanks guys. I'm thinking it's something between the switch and the thermostat as well. Not figuring why it didn't flip the breaker or if it's just a bad thermostat or..... I will start running it down tomorrow (I hope) with voltage on it and see if that tells me anything.

[chuckster57]

Be very careful playing with live voltage around a WH. Better off flipping the breaker and just test for continuity. I watched a guy smoke his meter trying to test for voltage at the thermostat when he shorted out the lead.

[sourdough]

Originally Posted by chuckster57

Be very careful playing with live voltage around a WH. Better off flipping the breaker and just test for continuity. I watched a guy smoke his meter trying to test for voltage at the thermostat when he shorted out the lead.

Thanks Chuck. I fried a meter myself about 45 years ago but I think I've got it covered (I hope). I hate messing with loose ends and big metal things when it's hot. I do appreciate the heads up.

[chuckster57]

Well post your findings, At least wear gloves.

[sourdough]

Originally Posted by chuckster57

Well post your findings, At least wear gloves.

Thanks my friend. I used to work aloft with heavy electrical gloves but can't feel/do anything with them. Once worked on an old glass screw in fuse panel for my uncle in the middle of nowhere standing on an aluminum step ladder wearing those thick rubber wading boots....ah, the good old, stupid, days.

[ChuckS]

If you also have an “Inside” switch in your panel to turn the electric s8de of the SW12DE water heater on .. then I’d be checking the remote relay that’s in between the heating element and that switch .

It may be melted

[bobbecky]

If the contacts in that switch were bad, they could have easily caused the heat that melted the wires at the back of the switch. You can splice them together to eliminate the problem as the switch is not a needed part if you have the 120 volt breaker in your panel that controls power to the electric side of the water heater.

[ChuckS]

I’d be more concerned about the remote relay switch being melted if he has an inside switch for electric operation..

[sourdough]

Originally Posted by ChuckS

If you also have an “Inside” switch in your panel to turn the electric s8de of the SW12DE water heater on .. then I’d be checking the remote relay that’s in between the heating element and that switch .

It may be melted

Chuck, where is this remote relay located? I'm going by the diagram below which does not show a remote relay;

https://s3.amazonaws.com/gs-geo-imag...f14cac20_l.jpg

[travelin texans]

Originally Posted by sourdough

Chuck, where is this remote relay located? I'm going by the diagram below which does not show a remote relay;

https://s3.amazonaws.com/gs-geo-imag...f14cac20_l.jpg

Danny, check under the black cover for the thermostats, mine had the wires pinched between the metal & the tank shorting them out.
Had to replace the tstats, splice more wire with new space connectors, bent the metal & trimmed about a 1/4" off the black cover. The very next morning my buddy parked next to us had the very same issue with the wires pinched.

[CampNBrew2]

Does the full current from the element travel through this switch? I've seen faulty switch contacts cause this, and more often bad terminal connections. When the wire was stripped they used the wrong gauge and stripped away wire strands. This effectively makes the wire much smaller gauge at that connection point and it overheats.

[Javi]

Originally Posted by sourdough

Chuck, where is this remote relay located? I'm going by the diagram below which does not show a remote relay;

https://s3.amazonaws.com/gs-geo-imag...f14cac20_l.jpg

I'm thinking he's talking about a second switch inside the trailer.. I have one in the control panel.. but I don't have the In-Command (thankfully)

[sourdough]

Originally Posted by Javi

I'm thinking he's talking about a second switch inside the trailer.. I have one in the control panel.. but I don't have the In-Command (thankfully)

Yes, I have the switch in the control panel and one on the tank. No in command thankfully as well. In the bit of troubleshooting I've done this morning I don't have AC to the switch which should be a straight shot back to the panel. I'm about to pull it out.

[sourdough]

Well, not so good. Pulled the panel cover; 120vac there and the breaker works. Looks good inside but I get a faint hint of smoked something. Empty the pass thru and get in the basement...arggggh.

[chuckster57]

I’m beginning to think a bad connection at the WH junction box.

[sourdough]

This story isn't ending the way I figured.

Pulled the cover in the basement and it is a maze/mess of wiring etc. No visible issues but; the feed line for the wh leaves the power panel 12/2 grd. It arrives at the switch/wh as individual wiring. There is a transition somewhere that was not visible from my perch. I was not going to crawl in there and tear up who knows what. The next step appears pulling the hwh to see what has happened and gain access through that hole. I won't be doing that. Danny I did check the wiring to the thermostats and it was OK.

It is still under warranty and it has to go back in when we return for the replacement of the back window among other things. I'll add this to the list. We have the gas portion so that works fine with the 12 gal. tank.

Sorry I didn't post a final resolution. If it was out of warranty I would pursue but not knowing what has happened will just let them deal with it in due course. I will post the findings once done. Thanks for all the help.

[Brentw]

Making some guesses and assumptions. At some point near the hwt, the house wire connects to the hwt factory wire ( you already guessed this) . That wire is in my opinion, barely adequate, but will do the job as long as there are no issues. That phoney little switch, while rated for the load, breaks down and causes a high resistance in that line, thus the melted wires. I do not believe the duty cycle on that switch supports very many cycles of switching under load.
I have been considering some changes to that circuit and eliminating that little rocker switch.
Good luck in your repairs.