AC not coming on after changing thermostat

Old 09-13-16, 07:17 AM
Thread Starter
Join Date: Sep 2016
Location: United States
Posts: 1
Received 0 Votes on 0 Posts
AC not coming on after changing thermostat

Hello all,

I am in the process of replacing the thermostat on a split type ac unit. I bought a standard programmable thermostat but after taking the old thermostat apart I can see that the set ups are very different.

On the current thermostat, the white goes to a screw on the thermostat board with X1 printed on the board. Blue goes into a screw on the thermostat board with X2 printed on the board. And those are the only two that go directly to the thermostat board.

Behind the thermostat inside the wall, there are two wires that are like the blue and white wires (Meaning they have the single cooper metal stick coming out of them). And two fatter wires that don't look like the other thermostat wires (Meaning they have a bunch of tiny wires bunched up).

The yellow wire with the single copper end has the blue fatter wire wrapped around it. And the green wire with the single copper end has the yellow fatter wire wrapped around it.

The red and brown thermostat wires aren't plugged into anything.

I have a standard Honeywell programmable thermostat that has letters for each color (Except for the brown cable). I hooked all them up but the ac doesn't come on (Note that I did not try and hook up the two fatter wires during this process).

I have not been able to see a set up like this online so I was hoping someone can assist with this

Any assistance would be appreciated. If you need more info then please let me know and I will provide it. Below is a picture of the current set up. Thank you!

Here is a picture of the setup:
Name:  NkZkpj.jpg
Views: 218
Size:  40.9 KB

Last edited by PJmax; 09-13-16 at 11:11 AM. Reason: added pic from link
Old 09-13-16, 07:35 AM
Bob14525's Avatar
Join Date: Jun 2013
Location: USA
Posts: 1,631
Received 30 Votes on 25 Posts
What is the make/model of the old thermostat that you're trying to replace? I'm not an A/C tech, but I've never seen a thermostat with just 2 terminals (X1, X2) before. All the thermostats I've seen have "conventional" terminals Y, G, R, etc. You may have to check the wiring at the air handler to see what terminals & wire colors are connected. That should let you "map" the wire colors to the appropriate terminals on the new thermostat. Is this an A/C only, a furnace with A/C, or a heat pump?
Old 09-13-16, 09:37 AM
Geochurchi's Avatar
Join Date: Nov 2012
Location: United States
Posts: 5,084
Received 96 Votes on 89 Posts
Can you determine where the wires are connected on the other end? That thermostat looks like it could be a remote sensor for another thermostat somewhere else in the house.
Old 09-13-16, 11:05 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,715
Received 1,616 Votes on 1,488 Posts
Welcome to the forums.

That looks like it's a communicating thermostat. It may or not be able to be changed depending on what's at the other end.

We're going to need the model number off that stat as well as the make and model number from your air handler.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: