Suburban SW12DEL Water Heater On/OFF switch melts???

[joebedford]

I know similar threads cover close to this subject, but they're old and don't quite answer my question.

I have a 2011 5th wheel. Last winter (I'm a snowbird) the switch on the heater failed (melted) so I ordered several and replaced the switch. It worked for several months until it was time to go home. When we came back south in December, the electric heater worked for a couple of days then quit. Propane still works. I immediately went to the switch and it was melted so I replaced it again. It worked for exactly one day then quit. I haven't taken the switch out but it's stuck in the ON position - probably melted again.

The old threads say the little switch doesn't carry the full current of the heating element but looking at the Suburban wiring diagram it appears to me that it does:

FYI none of the high temperature buttons has popped, nor the breaker tripped.

Any thoughts on what could cause this? I've already considered that I bought a bunch of cheap switched that can't carry the stated load.

Thanks, Joe

[QCMan]

Your best bet is to eliminate the outside switch if you have an indoor one. Using it as a "fuse" is asking for trouble as the overheating and melting can cause fires if things go wrong. Unless it is a heater, nothing electric should be hotter than what you can hold in your hand. Best to eliminate anything that causes unacceptable heat.

[QCMan]

Had that issue on a Starcraft that I had. I removed the switch and moved the wiring to the side of the vanity with a box and switch that had a light that went on when the electric side was energized. Never had to go out in the rain again because I forgot to turn the wh on. Used aluminum duct tape to seal the switch hole. Did the same as soon as I got the next one. Current one came with interior control of the electric side.

[joebedford]

OP here: mine also has a lighted switch inside the rig. The switch on the water heater is always ON.

If I have another problem I'm thinking of removing the switch on the water heater as I never use it. OTOH, better for the switch to be the fuse than wires.

The heater has been working fine for several days. After it's been in there for a week or so, I'm going to heat a full tank of water then cut the power and pull the switch to feel if it's hot. Hopefully the new connectors solved the problem.

[hawkeye-08]

I would change the element also. Perhaps it is drawing more current than the setup is designed for. You could also use an amp meter to see how much current it is drawing. 

[opnspaces]

Kind of sounds like they are saying "Yeah, maybe powering the refrigerator straight from the switch wasn't such a good idea after all. Let's add a relay"

[joebedford]

Suburban says the new SW12DEL units don't have an ON/OFF switch at the heater itself - power goes through a relay not the little switch. Maybe if I have more problems I'll wire a relay into the circuit so the switch doesn't have to carry much current.

[opnspaces]

I don't see the second schematic. But based on your first schematic I would try disconnecting the black wire right at the upstream or switch side of the Hi-Limit. Then turn on the switch and see if it lights up. If it does light up then there is a relay somewhere allowing the switch circuit to ground. This is expected for a relay and should not cause any melting. My thought is by disconnecting the Hi-limit and thermostat and heating element you isolate and remove all potential load from the circuit so you are only looking at and troubleshooting the control part of the circuit.

But if the switch does light up and then heats up I would be looking for that relay.

[joebedford]

This is what I put in to replace the burnt switch and I also replaced the somewhat burnt connectors.

Suburban sent me a new manual and it shows the high current flowing through a relay which is what I would have expected, but the switch does not appear in the schematic????

[joebedford]

I was going to show a photo of the switch I put in but this stupid website says "You don't have permission to upload photos" despite the fact that's exactly what I did to start the thread.

Anyway, I replaced the switch (it says 20A) and the connectors that were a bit burnt. 

So far it has worked for an hour - we'll see what tomorrow brings.

[joebedford]

The Suburban spec sheet says the circuit draws 12A. The bag that the switches are in says they can carry 20A at 125VAC. The switches have molded into the case 15A.

[Krusty · Accepted solution]

How is the wiring connected to the switch? Is there some type of connector? If so, perhaps the connection is becoming loose or building up resistance. Make sure connections are clean and tight too.

[joebedford]

I put new connectors on the wires and installed the new switch a couple of weeks ago. We've been using the water heater regularly ever since (on demand - we never leave it ON all the time). Today I pulled the switch and looked at it and the connectors - there's no sign of any melting or other issues, so I guess it's fixed. Thanks all for you help and thanks Krusty for suggesting it might be connectors.

[MNtundraRet]

If you do not have the specifications sheet from Suburban, I would check online for your model. It seems obvious that you purchased switches that cannot carry the heavy current..

You have a rather dangerous situation with no fuse blowing.