RTH2520 Thermostat backlight

I have not seen this issue and the manual gives you the option of either off or dim to high upon key depress.
Manual:
0280 Backlight 0 Backlight on for approx. 8 seconds after keypress 1 Backlight always on low intensity, full bright after keypress (requires 24VAC connection).
I am sorry I can not offer any further info.

Are you referring to the thermostat? If so pull it off the wall and see if it has battery backup, most all do.

U replace it.

Hi
Any short circuit on the PCB due to water intrusion causes short circuit in the supply voltage to the back light.
Try to clean the PCB under a microscope.or replace the damaged parts.

Try to replace inverter board

sounds that way, yes.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

• Display Backlight - (Not available on earlier models.) The display backlight improves display contrast in low lighting conditions. Selecting backlight ON will turn the light on for a short period of time after any button is pressed. Selecting backlight OFF (default) will keep the light off. Turn the display backlight feature ON as follows: 1. Press TIME and RUN buttons at the same time. The display will show "d-L" and "OFF" alternately

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.

After posting that I was having the same problem, I found a solution.
I used these instructions http://www.hydro-temp.com/help/drawings/honeywell%2069-1894ES.pdf and followed the Installer Setup on pages 6 through 10. Basically you just need to enter the setup mode following the instructions, scroll to setting# 280 and change the setting from "1" to "0" then the backlight will turn off after 8 seconds. Don't change any other settings if you don't know what you are doing.


If you need further help, I’m available over the phone at https://www.6ya.com/expert/jeffrey_634abadf963e31e5

Hey Dannes1956,

The Motorola V3m has a light sensor, which is visible just above the right soft key -- the key above the CLR button. This light sensor turns the backlight on when you press a key in the dark and disables the keypad backlight when you are in a well-lit area.

Your phone sounds like it's operating normally. I believe they disabled the option to activate or deactivate that feature.

Hope this helps,
cHiPz.