Need assistance with Decoding the wires from our HVAC unit to our Thermostat


Old 05-27-14, 03:08 PM
Thread Starter
Join Date: May 2014
Location: USA
Posts: 3
Need assistance with Decoding the wires from our HVAC unit to our Thermostat

We upgraded our thermostat last October and didn't record the wiring or save the old thermostat. Our heat worked great, but now the A/C doesn't turn off and we've deduced that it's a wiring problem.

We have a Carrier Performance 80 that we can't find online diagrams for and when we emailed the picture in the unit to my father-in-law, he says it's missing information.

The new thermostat is a Honeywell RTH2300.

The wires inside the wall are Orange, Green, Red, White, and Blue, but the Blue wire isn't connected to anything on the HVAC end.

There are two groups of wires coming from the HVAC. Green and Yellow. Yellow, Green, Red, White, and Blue. The two yellow wires are connected. The green wire paired with the yellow is connected to the orange. The Green paired with the other wires is connected to green, red to red, white to white, and blue is hanging out.

Unfortunately, the image uploading keeps failing.
Sponsored Links
Old 05-27-14, 03:31 PM
Bob14525's Avatar
Join Date: Jun 2013
Location: USA
Posts: 1,444
Likes Received: 4
I'm somewhat confused as to how many wires are going to the thermostat. You mentioned 2 yellow and 2 green wires. However, assuming the wire colors are connected to the furnace in the conventional order, here are what the wire colors are:

Red is the 24VAC going to the thermostat, coming from the transformer
Yellow is the wire going to the compressor (outside A/C) unit and controls it's operation
White is the wire that controls the furnace operation (heating unit)
Green is the wire that controls the operation of the air handler (blower)
Orange or Blue is used for heat pumps and controls whether the unit is operating in heating or cooling mode

Whether your system is wired per the "standard" color coding convention is anybody's guess, but if it is, the above information tells you what each wire does.
Old 05-27-14, 03:57 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,518
Likes Received: 105
At T.stat
Orange = Y
Green = G
Red = RC/Rh
White = W/B
Blue = no connection

You need to explain a little better what your connections are.

"There are two groups of wires coming from the HVAC".... What's the HVAC ????

There should be one cable from the thermostat to the furnace and one cable from the furnace to the compressor unit.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes