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Can someone look at wiring of my thermostat and HVAC panel? I don't understand why R wire is connected to RC at thermostat. I am also not sure why Y wire is not connected at HVAC panel.

Here is my problem and some facts.

  • My thermostat display stays blank.
  • Heater continuously stays on.
  • I never had problem with AC (although Y wire is not connected at HVAC panel)
  • Model # Honeywell CT3650
  • I tried replacing brand new battery, but display won't turn on.
  • This is not new installation.

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  • It would be useful if you provided make and model of your thermostat. Also is this a new installation? If so, how was the original thermostat wired? – Barry Nov 13 '19 at 23:43
  • Can you post photos of the wiring at the air handler? – ThreePhaseEel Nov 14 '19 at 0:13
  • Model is Honeywell CT3650. I will post photo of wiring at HVAC panel tomorrow. Thank you. – user2716454 Nov 14 '19 at 3:58
  • I posted picture of HVAC panel wiring – user2716454 Nov 14 '19 at 14:07
  • 1
    The Y wire can go directly to the outside unit and is not always connected to the air handler. There might be another wire junction where that happens and that wire junction could have a problem (bad connection, rodents, etc). – JPhi1618 Nov 14 '19 at 19:19

It looks like there is a jumper between the R and Rc so it doesn't matter which screw is used. Nothing shown here gives any indication why your display is not working.

  • Is this jumper hidden inside thermostat? I thought it will be visible if there is one. I changed batteries but still display won't turn on. my heating system stays constantly on. Must be bad thermostat. – user2716454 Nov 14 '19 at 3:54

Thermal display blank because it doesn't have power. this shows it needs 3 AA battery https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1285.pdf

. You should remove all the wiring then insert the batteries. It should display before any wiring.

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