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I tried installing a honeywell thermostat but found out i…

Customer Question
I tried installing a...

I tried installing a honeywell thermostat but found out i only have a red and white wire foing to old thermostat i have no common lead

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

I dont have a common wire to hook up thermostat i gotta run a common wire off the furnace but no idea where the line is

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

Yes

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

I know how to run the wire but problem is where does the common wire supposed to hook up on this model

Submitted: 8 months ago.Category: HVAC
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Answered in 2 hours by:
11/25/2017
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,614
Experience: 40+ yrs. experience as a licensed oil & gas technician.
Verified

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. First I’ll need some more info so I have a more complete picture of your situation.

What is the brand and model of your furnace?

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Customer reply replied 8 months ago
1976 lear seifler
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Finding a common on a 41 year old furnace (I assume this is a furnace not a boiler) is going to be a challenge. I'll need a picture of the wiring diagram. It's usually pasted to the back of one of the access panels.

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Customer reply replied 8 months ago
As many pics there i just need to know witch wire is the common or where to splice the wire for the common wire to run
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Transformer in your first pic has 1 lead connected to thermostat wire. Your common is the other transformer wire. It's connected directly to the gas valve. You can splice into that wire.

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HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

I have to step away for about an hour. If you have more questions I'll respond when I return. If not I'd appreciate a favorable rating. The thread won't go away and I'll answer related follow up questions even after you rate me favorably

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Customer reply replied 8 months ago
That is the black wire on it
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

The transformer has 2 black wires. You want the one connected directly to the gas control valve.

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Customer reply replied 8 months ago
It does not turn the heat on or fire up the heater it does turn on thermostat but doesnt ifnite burners when its supposed to go on
Customer reply replied 8 months ago
i can just touch the red and white wires together and poof it will start up
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

If the thermostat is powered up then you wired the common properly. If you have it set to heat then it should fire up the burner if the thermostat is calling for heat. I'm assuming you have red to R and white to W. Beyond that I don't know what you did to set up the thermostat and that was not the question you asked. You asked how to wire the common and I gave you the appropriate answer. You could try he Honeywell help line for set up issues.

I'd appreciate a favorable raring

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