Solution to this problem. When you update your system from single stage to 2 stage, you must have C wire from outside unit. My old single stage system came with 3 wires from outside unit to indoor (blower) and Indoor unit to thermostat had 5 wires. I solve this problem with new wiring the whole house. I install 4 wires from outside unit to indoor (blower) (red(Rh), blue(C), yellow(Y1), purple (Y2) (mine had a purple)); Indoor unit to thermostat install 7 wires, which following below. red (Rh) blue (C) yellow Y1 Cooling stage-1 Gray Y2 (Purple Y2) Cooling stage-2 Green (Fan) white (W1) Heating stage-1 brown (w2) Heating stage-2 If you don't want to rewire, I recommend to get CTK04 thermostat, which will be fine with your old wiring.

OK, folks, I met with the owner of Fort Collins Heating & Air this morning. He seems to live up to his reputation of being a stand-up guy. I told him that I was going to talk with him this morning, then with a competitor this afternoon, then get back to both of them tomorrow morning with a decision. So I would massively appreciate your thoughts on which course of action to take. I told the FCHA owner that if I decide to keep my existing system, this is what I would want them to do: Have their best team replace the humidifier and go over the system from top to bottom. Replace the thermostat, too, if they can't make the low-battery symbol go away, given that I just replaced the batteries last week. Extend the first-year tear-it-out warranty to March 30, 2019. No charge for repair calls from now to March 30, 2019. Free furnace inspections in Sept. 2018 and Feb. 2019. If I want the system torn out with a full refund at any time between now and March 30, 2019, FCHA tears out the system, no questions asked. The FCHA owner said he's pretty sure he could agree to all of those conditions. I then met with a sales guy from another HVAC company that also has a solid reputation. Here's his proposal: 96% up to 97% 2-stage heating, variable speed motor. 16 SEER A/C system. 1-stage cooling. : Installation to include: Finish the mastic sealing in the mechanical room per code. All necessary PVC venting needed. All 220v, 110v, and 24v electrical needed. Condensing unit outside. Evaporative coil inside. TXV (thermal expansion valve). Refrigerant lines from inside out. All installed. Task HCS-PH60. Premier Amana Two-Stage variable speed gas furnace. 96% AFUE. Stainless steel tubular primary heat exchanger. Efficient and quiet variable speed circulator motor. 10 year parts and labor warranty. Limited lifetime “unit replacement” warranty on heat exchanger. *Annual maintenance required. Price: $6,682 Task D-F750 $750 off high efficiency furnace Task HCS-DC30. Deluxe Amana high-efficiency air conditioner. Up to 16 SEER. High-efficiency scroll compressor. Single-speed condenser fan motor. Limited lifetime “unit replacement” warranty on compressor. 10 year parts and labor warranty. Lifetime limited “unit replacement” warranty on heat exchanger. *Annual maintenance required. Price: $6,024 Task D-AC750. $750 off high-efficiency A/C Task HO3. Bypass evaporative humidification. Can be installed on supply or return. Works only while heat is cycling. Not recommended for home over 2500 SF (My home is about 3,800 SF, including partially finished basement). Price: $895 Task D-HSHUM. Free humidifier with purchase of high efficiency furnace or AC system. Task ACO4. (Air cleaner, I assume). Honeywell 4” disposable air filter. Merv 8 filter rating. Uses no electricity, but requires replacement media quarterly. Price: $895, but free with purchase of high efficiency furnace or A/C system. 5 year parts and labor warranty. Task TS-EC4. (thermostat/humidistat, I assume). Comes with built-in Alexa Voice Service, so you can ask your ecobee to set a timer, read you the news, etc. 5 year parts and labor warranty. Price $0.00 Task ACO7. Return air box (square – 14, 17, 21, 24) includes easy 1” filter access. Improves air flow efficiency by up to 25%. Price: $0.00 Task SD-100. Senior discount. $300. Cash or Check discount. $100. If I have it installed 3/8/18 (may not be feasible): $350 discount. Total: $10,566 All of this partly depends on the current supplier leaving all water supply lines and electrical. Otherwise, it may cost me about $500 more, according to the sales guy. Given your HVAC knowledge, what would you do if you were in my position?

WHAT IS A HIGH LIMIT SWITCH? https://www.newcentralairconditioner.com/ The high limit switch in your gas furnace is a small part with two very important jobs. This switch plays a role in the normal operation of your furnace. Turning the fan motor on and off is the high limit switch’s main job. This is the role it plays in every cycle of your furnace’s normal operation. But that’s not the only thing that the high limit switch does. It’s also safety device that helps prevent your furnace from overheating. The high limit switch consists of a long temperature-sensing probe attached to a metal mounting plate. From the mounting plate, the switch is wired to the blower fan motor and to the gas valve. The switch is generally located just past the heat exchanger. This is so that it can detect the temperature of the supply air. In other words, the air that’s about to be blown into your home.

First, the batteries are typically just there to keep time and any programming in the t-stat in case power goes out. They won’t run the display. If you only have 4 colored wires, then most thermostats made today won’t work because they require a 5th wire, typically black blue or brown, to be used as a common wire because the thermostat actually draws power to run itself. You will need to find a thermostat that doesn’t need the 5th wire or you can run the 5th wire yourself if it is not too hard. The fan switch doesn’t depend on any relays inside the thermostat to work, so when you switch it to “on”, you are physically connecting the red wire incoming 24 volts a/c to the green wire. When the furnace gets 24 volts back on the green wire it turns the fan on. It sounds like the thermostat is dead since nothing shows on the display. I would suggest trying to find the same model # thermostat on eBay and just swap it out.