I have a combination gas and electric/DSI Atwood water heater (model GE16TE) that has been working fine but suddenly died this morning. Wouldn't work on gas, electric, nothing. Checked all the fuses, checked for flue tube obstructions, checked wiring connections, etc. but the problem persisted. Finally called Atwood on the phone (very nice people) and was immediately connected to a friendly service tech who walked me through a diagnostic process that quickly located the problem- I had a fused Thermal Cutoff. This cutoff detects high temperatures due to an obstructed flue and once fused will prevent operation in either gas or electric mode. Since my flue wasn't restricted I wondered why the Cutoff would be fused- the tech said that it happens occasionally when both modes of operation are selected, i.e. gas and electric are on for the quickest water recovery time.
Unfortunately once the Thermal Cutoff activates it has to be replaced (it basically acts as a fusible link) but the water heater works fine without it and Atwood has shipped me a new one at no cost under warranty.
If your water heater dies, here's a quick way to find out if it is the Thermal Cutoff. First, MAKE SURE there are no obstructions in the flue tube. Then turn off the water heater's electric mode and turn on the gas mode. With the exterior access door open and looking at center of the water tank you'll see a black foam-covered area with 4 wires running to it. Look for the area marked T-STAT with two brown wires running to it. One of the wires will have a piece of clear tubing over it that covers a large diode- this diode is the Thermal Cutoff. (Mine didn't look burned or in any way defective, so a visual inspection won't tell you if it's bad or not.)
Remove the diode from the T-STAT terminal lug then disconnect the other end of the diode from the brown wire connector. Now connect the brown wire (without the diode attached) directly to the T-STAT terminal lug. Give it a few seconds and the water heater should turn on in gas operation mode. If it does, that means the Thermal Cutoff is bad and you'll need to get a new one from Atwood. Leave the wire hooked up, turn on the electrical mode to supplement gas mode (if you want) and you'll have hot water till you get the new Thermal Cutoff.
If the water heater doesn't turn on after a minute or so chances are it's not the Thermal Cutoff and you'll have to look elsewhere for your problem.
This is just one of the reasons why I love this forum. I will print and put in my folder for the water heater to keep for future reference. Thank you so much for sharing this information, it may come in handy someday.
Good post but some corrections needed. 1. The Thermal Cutoff has no affect on 110 operation. ECO switch is the High temp cutoff. The Thermal cutoff is for flame blow back on LP operation. Either the burner is obstructed or high winds have blown the flame back and the Thermal cutoff will "burn/melt" and stop current to the gas valve. Brent
I'm pretty sure that the device shaped like a diode you're talking about is a 'chem fuse'. I've found them on my '94 Atwood and on brand new ones too. This is a bi-directional device (for AC or DC operation) that is used as protection in all sorts of electrical devices, like coffee pots and irons and such.
It has the property of opening like a fuse under several conditions: current too high, such as caused by a short circuit; chronic over heating caused by a minor short circuit or miswiring; or external heating, caused by a fire. They differ from regular fuses by being sensitive to fire. Regular glass fuses can resist fire for quite a while.
These devices are shaped like small bullets of about 1/2" long and 1/8" diameter with green glass at one end, a metal case and a solid metal wire coming out of each end.
The devices have been around for many decades and can be found at many electrical supply houses such as 'Radar' on the west coast and at others. They are a couple bucks each and are ordered by their temp rating...stamped on the device.