Thermostat it's hot!! :<)


Old 06-17-07, 05:06 PM
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Thermostat it's hot!! :<)

Last fall my father in law and I replaced an old manual Honeywell thermostat (round,bronze) with a new programmable Honeywell. The old thermostat was working fine but was in the lower level and we wanted a programmable on on the main level. At the time we hooked it up we tested the heat and the furnace was working. He did mention that as something within the new thermostat needed to be jumped and he was not sure if that was done correctly he questioned whether or not the AC would work come summer. Well,summers here and it won't come on.

Rather than delve into getting the new thermostat to work I decided to just reconnect the old stat. We had left all the wiring in place. I hooked up the W,Y,R,G wire to the corresponding terminals and it doesn't work. Don't know why.

We currently have a vertical strip with (from top to bottom) W,Y,R,G,C terminals. I believe only the WYRG were hooked up with the old one and that's all we hooked up with the new one. There is a wire coming from the other side which has a Red wire connected to the Y terminal and a White wire connected to the C terminal. I'm not sure where they come from or what they do. Do they come in from the AC unit outside perhaps.

I realize this was a lot to digest. Any thoughts or theories will be greatly appreciated. Thanks!

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Old 06-17-07, 07:02 PM
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You saying that you put the old t-stat back on, and still don't work?

What it the model and make of the new t-stat?

When you changed out the t-stat, did you turn off the power at the furnace?

On some t-stat, you need to put a jumper between R(c)/R(h).

The two white and red wire are coming in from the out door unit.
Old 06-17-07, 11:03 PM
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If your new thermostat has batteries it may not need the C terminal. If it worked with the heating system it should work with the cooling system.

The "standard" color code for thermostats is:

R= power from the furnace to the thermostat
G= power from the thermostat (red lead) to the fan relay in the furnace
W= power from the thermostat (red lead) to the furnace heating control
Y= power from the thermostat (red lead) to the outside A/C unit

These wire connections will be at the thermostat and at the terminal board in the furnace. The two-conductor wire from the A/C outside unit will connect to the Y and C terminals in the furnace, color is not important.

Your thermostat MAY have two R connections either R and Rc or Rh and Rc (possibly RH and RC). There needs to be a "jumper" wire connecting the two R terminals.

What model Honeywell thermostat do you have?

If you did not shut off the power for the furnace BEFORE changing the thermostats / wiring you may have blown the fuse in the furnace.
Old 06-18-07, 04:33 AM
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First do you have a 4 or 6 or 8 Thermostat leads going to your new thermostat?
Many furnaces only have 4 lead colors going to the thermostat and program gas thermostats should have 5 lead wires

You state the new program thermostat works in Heat but not in Cool?
Does your fan run when it's turned to the On position right now?

You also state you did not hook up the Common terminal? If so then the new Tstat runs off batteries. I do not recommend running a thermostat just from batteries.

If you have an extra thermostat wire in your thermostat cable connect the C terminal on the thermostat to the C terminal on the vertical strip by/in the furnace. Normally the color Brown is used for common. Be very careful with common, You can screw up any other terminal and just get a funky result but you can blow a fuse or a transformer if you miss wire the common terminal. (Short to ground)

Also I gather you moved your thermostat from one level of the home to the other so you ran new thermostat wire to the main level location? Did you disconnect the old Thermostat wire in the lower level at the vertical strip Furnace? If so then that is why the lower level does not work right now.

Also like Furd said,
I would put the Yellow wire from the Tstat to the Red Wire from the outside unit to the Y terminal on the vertical strip.
I would put the white wire from the outside unit on C
remember if you hook up the programmable thermostat common terminal go from the C terminal on the stat to the C terminal on the vertical strip that should have the white wire from the outside unit hooked up to that.
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