Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

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RTH2520 Thermostat backlight

Backlight on our thermostat stopped working. I think that everything else works fine. Is there anything that I could do my self to get it to work again? I got this unit at Costco in November 2008 and installed it my self.



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  • Anonymous Mar 29, 2014

    Doesn't work long


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Some thermostats have batteries i have found that they sometimes have enough power to operate t-stat but not back light. usually AA batteries other than that it is more than likely a problem that can not be repaired

Posted on Jan 05, 2009

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Multiple issues that are not related. If the pilot light goes out then the thermocouple might be bad. If the pilot ignites the gas and everything shuts off, it sounds like the over temperature sensors are detecting heat in excess of what is allowed in the firebox. The thermostat issue has nothing to do with this.

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Make sure to purchase a thermostat that will operate on a millivolt system the old Honeywell t-87 would work but the new T-87 replacement ones do not work. make sure the wires are not touching each other at the connection points. Hope this helps.

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If it has a manual control,not digital,remove the control panel,and remove the thermostat,and use a finger nail file,and file the contacts in the thermostat,the points,contact points.This is about all you can do,if it is anything else,throw it away,and buy a new one,the parts are as high as a new heater.If it is a digital control,throw it away period,cost to much to repair.

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Relatively new wall furnace suddenly stopped working.

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Jan 13, 2010 | Heaters

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No digital readout on home thermostat. No backlight either.

Turn the Furnace off, Disconnect the R and W thermostat wire from the control board located usually in lower compartment of furnace, the blower
is usually mounted behind it.

Make sure the 2 wires you disconnect are going to
R(usually power) and W(usually Heat) other terminal
markings are y(for cool) g(for fan). After Disconnecting the R and W wires Turn the furnace
back on. You will probably have to hold a door switch
in to complete the circuit. If everything is correct the
furnace should not run.

This is more than likely that you have the R and W
wires touching eachother and you need to get them seperated.

Jan 05, 2010 | Heaters

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