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In a bathroom I have a single 500w 240v electric baseboard heater, and AUBE/Honeywell TH305 digital line voltage single pole thermostat.

I noticed yesterday, that the display had gone blank. A quick check showed there was still power to the stat. I tried switching it with another one from another room with no luck.

I checked for power at the heater (which there was), and then tried switching the heater in case a faulty thermo sensor was the problem. Still no luck.

So now I have power at both the stat, and heater, but still a blank display...

All the other heaters in other rooms on the same circuit work fine.

So now what?? Could it be a voltage problem? If so, how was it working before? How would the voltage change??

Any help or input would be much appreciated!!

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  • Changing the stat was the first thing I tried. I switched it with one that was working in the next room. The stat in question also worked fine in the next room...That's part of the mystery...
    – FYuhas
    Feb 4 '16 at 1:54
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i know this is an old thread - but i saw it and it helped me think through my problem, so I thought I'd share what i found since it seems the solution never got posted.

same exact situation - thermostat screen was blank a few months after installing a new 240 V baseboard heater, wiring, and thermostat. I changed the "bad" thermostat for a new good one, and the new one was blank, too, when i powered it back on. My voltage tester showed power coming into both wires at the thermostat.

i started reading the manual for the thermostat. it states that the screen can go blank if the 'overheat' fuse in the baseboard heater activates, which made me start thinking that if there is an open at the heater, it can act this way.

turned out I had an open circuit at the heater, itself. One of the wires into a wire nut inside the heater had come loose. I reinstalled the wire nut, turned the breaker back on, and all was right with the world. I felt stupid for not figuring it out before swapping out the thermostat - at least it only prob wasted me 30 min and $18. (too embarrassed to return the new thermostat for my mistake...)

hope that helps someone else.

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Sounds like a dead thermostat.

When it was working before, it hadn't died yet.

Why it died is likely to remain a mystery. Things don't live forever (neither do people - dragons might, per one song.)

Replace it.

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  • 1
    Yeah, something inside the stat went belly up. Feb 3 '16 at 1:15

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