trying to install smart thermostat

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Old 09-15-19, 07:11 AM
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trying to install smart thermostat

Issue: I tried replacing my thermostat with a smart thermostat and now air conditioner will not cut on with old thermostat and smart thermostat will not turn on using C wire. Indicator LED light flashes 1second on and 1 second off, so air conditioner does not show any error codes.

backstory:
I got my air conditioners replaced a couple years ago. I specifically asked for nest thermostats, but when installing he said he couldnít install them because i needed 4 wires and there were only 2 😡. So he installed battery powered non WiFi Honeywellís. He had already installed them and did not give me any option he could do on his end to get the smart thermostats installed.

anyways... I thought this sounded odd and just now got around to looking into it. I have a downstairs and an upstairs AC. Lennox brand. Downstairs AC has a bundle of wires, but only 4 are in use by old thermostat: R, G, Y, and W. Orange and black are there, but unused. I then went to circuit breaker and turned off ĎA/C 1í and ĎA/C 2í. I went in my attic and opened the air conditioner up. Turns out the air conditioner circuit breaker did not turn off my furnace in the attic and I opened it up while it was still on. At the time I did not realize it was still on. I went back downstairs and plugged the old thermostat back into the wall and the air did not kick back on. I then realized dumbass me did not screw the metal plate back on upstairs so I went back upstairs and put it back on and made sure the furnace was on. The status light showed a heartbeat and no errors. The A/C still did not kick on so I took the thermostat out again and let the capacitors drain so it would reset. I plugged it back in and still no luck. I am hoping I did not mess up anything. I did try to hook up the new smart thermostat, ecobee4, with C wire and it did not even turn on.
 
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Old 09-15-19, 08:10 AM
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Got it to kick back on

I installed the old thermostat again and the furnace kicked back on. Now I just need to figure out why the C wire did not turn on the smart thermostat
 
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Old 09-15-19, 07:42 PM
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Welcome to the forums.

Ok.... so you've established that you have extra wires that can be used for the C connection. Now you need to pick a spare color and connect it to C on the thermostat and C on the air handler.

If you can't find C at the air handler..... post a few pictures of the wiring for me.
How-to-insert-pictures.
 
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Old 09-16-19, 05:04 AM
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I think I diagnosed my issue, but not sure how to solve. I already have a C wire and itís already hooked up. I did try switching the C wire out for one of the spare wires in case that particular wire was bad or something, but did not work. R +C does not produce 24VAC

so, my old thermostat is battery powered and works just fine. But, if I remove R and G from my old thermostat and try to dry touch them, my fan does not kick on. So, I am wondering if there is something wrong with the R wire and itís not getting power or something. The R wire is hooked up to some sort of switch in the overflow tray before plugging into the air conditioner. Maybe that switch is bad or something? If my R wire is not getting power, could the battery in my thermostat be used to turn on the fan, A/c, etc?
 
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Old 09-16-19, 10:49 AM
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R is the 24v and is required for any function.
R to G turns on the blower.
R to W turns on the heat.
R to Y turns on the A/C condenser.

Without R present..... nothing will work regardless of thermostat.
R to C should yield 24vAC. Did you check right at the furnace board ?
 
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Old 09-17-19, 12:34 PM
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R wire

I have an R wire present, but R to C produces 0.07 VAC at thermostat and R to G does not turn on fan. What I do not understand is if dry touching R to G does not turn on blower, how is my old battery powered thermostat able to turn on blower? The only explanation I can think of is that R wire is not being supplied with any voltage. If thatís the case, either the furnace is not outputting 24v on R, the switch is bad, or the wire doesnt have good connection to either furnace or switch. The G wire just needs voltage from somewhere to turn on blower and a battery could provide enough voltage for it I presume. In that case, R wire could be swapped out by battery because R is just a power source. I am going to test this tonight I think to prove or rule out my theory by removing R wire from thermostat and seeing if it still works.

I have not tested at furnace because I have a switch in my furnace that turns off furnace when I open it up. I guess I could manually push the switch in just to get a reading, but I donít want to damage my furnace in the process. Would it be ok to keep furnace on while I have the back plate off?
 
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Old 09-17-19, 12:48 PM
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R wir

On further thinking... my thermostat should not bypass R wire because of the overflow switch. If my overflow basin fills up with water, then tstat should not turn on fan, A/C, or heat. So, thermostat should not work if I unplug R as you stated
 
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