Honeywell RTH230B 5-2 Day Programmable Thermostat Large - Page 7 - Answered Questions & Fixed issues

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.

Without seeing the wiring diagram, I can only say that the MV/PV terminal in many cases is used as the common from the thermostat/transformer. Usually, the 24 volts is supplied to the thermostat from a step down transformer and the thermostat sends voltage to the controller. I would hesitate to "guess" at this without a complete understanding of the wiring requirements. Any HVAC tech should be able to help you.

It has been my experience that the screen is damaged. You will most likely have to replace the thermostat. I have seen where heavy scratches will cause this condition.

So if the temp changes what are you wanting to change? I'm confused.

Typically the box will say "C wire required " Any 24v tstat will work, just make sure it doesn't say c required.

What's the model of your outdoor unit.

Hello Ed, Here are some links that are going to help you solve your problem. Good luck, JP

Hey Chris, Call Honeywell,see if they can help with that. 1800-468-1502 https://www.honeywellhome.com/en/faqs/thermostat

When you turn power on/off your resetting the entire system. The problem is your air handling unit or outdoor unit. Something is locking out the system. Would need model number outdoor unit/indoor unit. What breaker are you resetting? For what unit.

Help how do I unlock this?

And if what jumptrout51 said does not work, remove the thermostat to expose the wiring and place a jumper between (R) and (Y).

likely have a tripped float switch from a backed up drain line

It seems like since it's battery operated, you can still use the three wires only. R, G, and Y, and set thermostat jumpers or program accordingly. The batteries will operate relays, LCD screen, but if I'm wrong, then the C terminal would need to be used both at the unit and thermostat to power the thermostat with 24 volts, not likely, just use one of the spare wires you mentioned or preferably the black wire.

Use the r and w points for heat only. If it is a digital thermostat without a battery you may need to put a resistor between the w and c on the furnace to allow the thermostat to work properly. Your manual should tell you what value resistor.

You may need to set the thermostat to energize or de-energize the reversing valve. Essentially you possibly have it in heat mode. Or you wired it to energize emergency heat strips.

You most likely setup the thermostat for something besides heat pump function. What is the model number for the Honeywell thermostat and Coleman unit?

Did you check the batteries too? And do you have the temperature settings right for each program?

What is model of the Thermostat Did you check the Circuit Breakers to make certain you have not simply tripped a breaker? In general, depending on where you live: If you will need Heat select Heat then set the desired Temperature If you will need Cooling select Cool and then set the desired Temperature. Fan should be set on Auto.

press button below where it says unlock. Enter code...1234 press up/down button until you get 1 then press select. repeat until you get 1234 on screen then press select, should unlock it.

What does 2 flashes mean ?.
Maybe the controller is bad