I have a gc-tbz48 thermostat that has been in service a few years. Today I went to adjust the temp and got a shock from static in the house. Now the display says SENSOR and isn’t displaying the temp in the house. I tried a reset but that didn’t help. Any other things I can try?
Can you upload a photo of the screen? Is there anything else showing? The select and done buttons?
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Yes. Button selections show. I can go to menus and change items. However turning the fan on doesn’t do anything and obviously setting the temp does nothing as I guess there is no input from the temp sensor.
Does pressing the arrows cycle away from Sensor or does the display remain the same?
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Yes. I can move away from it. If I adjust temp I see that, if I go into menus I see those. Once any of those time out it goes back to this screen. The 2 dashes seem to be the room temp. Other than those being dashes and the sensor line above the thermostat allows me to navigate and set things. It just never turns on anything because there is no room temp.
I guess I could put my multimeter on the temp sensor and see if it’s getting a reading and then apply heat near it to see if the sensor detects the change. At least then I would know it’s the sensor and not some other electronic part that has died.
I’ve never seen that model simply display Sensor, and unless it is stuck in Sensor calibration in the menu, which it does not appear to be, it does look like a hardware failure of the sensing element.
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I used my multimeter and ohm tested the thermistor at location TS1 inside the thermostat and it is bad (I get no reading of resistance). I have a second and working one of these thermostats and did the same ohm test on the thermistor in it and get solid readings as I change the temp around it.
I put batteries in the good thermostat so I could see the temp reading on the display and heated the thermistor by putting my hand over it. Once I got it to 77deg F/25deg C, I tested the thermistor to get the ohm reading and it was right around 10k ohms. I also noted as the temp rose the resistance fell, which tells me it’s an NTC type thermistor. With that info I know this is a 10k ohm NTC thermistor. I’ll order a few and replace it in the damaged thermostat. They cost under $1 ea. so it’s well worth the repair when you look at the cost of the thermostat.
Hopefully this info will help someone in the future. Keep in mind this happened due to static electricity buildup and just touching the outside of the thermostat to change the settings.
Photos below show the location and part.
I will update when repair is done.
Wow, thank you for the detailed testing and follow up!
That’s definitely what I would’ve assumed the issue to be. Hopefully the repair will be successful. This may be beyond the ability of some users, but a cheap, effective potential fix for a specific problem is always very helpful.
Update:
I got my thermistors in and replaced the TS1 location thermistor with “Thermistor Temperature Sensor NTC MF52-10K 3950 ohm 1%”. These can be bought at most electronics parts suppliers like Mouser etc. This fixed my issue. So for anyone having my issue or anyone looking for info on what Thermistor to use for remote temperature sensing, that is the specs for that sensor.
Nice, thanks for the confirmation. Glad to hear you were able to fix it!