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We have a very old mercury nordyne thermostat that we are…

Customer Question
We have a very...

We have a very old mercury nordyne thermostat that we are trying to replace with a new Honeywell programmable thermostat and we can't get the old wiring to properly connect with the new system to make it run

Contractor's Assistant: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?

Specific to the thermostat

Contractor's Assistant: Do you plan on doing the work yourself?

Trying to now yes

Contractor's Assistant: Anything else we should know to help you best?

The old system was wired with 6 wires, blue, orange, green, yellow, white, and red

Submitted: 1 year ago.Category: HVAC
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Answered in 18 minutes by:
8/1/2017
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7,426
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Verified

Hello, tell me what color of wire attached to which terminal letter on the old thermostat and which of those wires you connected to which letter terminal on the new thermostat,

We can go from there

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Customer reply replied 1 year ago
We don't know which wires we're attached where on the old system
Customer reply replied 1 year ago
I can tell you which wires I have and which terminals are on the new system
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Send me a photo of the thermostat wires where they attach inside the furnace/ air handler and a photo of the wire attachments at the new thermostat

Use the 'add files' link next to your send button for that

Did you do this wiring with the power to the furnace /air handler turned OFF... if no you may have blown a fuse in the 24vac control circuit

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

I need the brand and model number of the new thermostat so I can pull the manual on it

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Thanks, disconnect and tape the wire used to go to C on the on the old thermostat

Run the wire that used to go to E on the old thermostat to W/Aux on the new thermstat

connect all of the other wires to the same terminals they were on the old thermostat as

marked Click Here please

Fortunately I see that you marked each wire with tape, that should made it easy

DO THIS WITH POWER OFF AT THE FURNACE AIR HANDLER

If you have not done that already you probably blew a fuse at the air handler printed circuit board, check for that.

We can go from there

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Customer reply replied 1 year ago
Trying this now
Customer reply replied 1 year ago
Still doesn't seem to be working
Customer reply replied 1 year ago
I set the functions
Customer reply replied 1 year ago
But it still never kicked on
Customer reply replied 1 year ago
Hello?
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

I must come and go on this end to handle an ongoing stream of customers, sometimes there is a few minutes delay.

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