Identifying Wires KJR-120G2 / TFBG-E-03

[PBDiggins]

Hi - I'm trying to install my first Nest Thermostat but not all of the wires on my current thermostat are labeled.  The model numbers on the board (KJR-120G2 / TFBG-E-03) seem to be generic and one manual online only notes the wires are red, black, yellow, and brown with no detail on what each one does.

https://www.beijerref-carrier.com/media/pdf/d5/3e/42/2017-02-Installation-and-user-manual-KJR-120G1-...

The control board notes +12V (red) and GND (black) but the other two wires aren't labeled.  The wires do not connect into the usual separate clips but are instead bundled into a plastic connector like you would see on many other control boards in a computer.

Does anyone have guidance on identifying the current wires?

[PBDiggins]

[Jake]

Hey PBDiggins,

Sorry for the late reply. I wanted to follow up and see I could be of any help. I found an article with more details on how to identify a wire. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further. 

Best regards,
Jake

[PBDiggins]

Thank you, Jake. Unfortunately I had seen that article and didn't find the answer there. I am talking to an HVAC specialist about checking the old thermostat in person.

[Jake]

Hey PBDiggins,

I am glad to hear you are speaking with an HVAC professional. They should be able to provide you with further details on your system and what the wires exactly are. Once you have found out the wire labels, I would be more than happy to assist you with getting the device set up. Please let me know once you have obtained that information.

Best regards,

Jake

[Jake]

Hey PBDiggins,

I wanted to check in with you, and see if you were able to get more details on the wires you are seeing. Please let me know if you have any questions from here, as I would be happy to take a closer look.

Best regards,

Jake

[Jake]

Hey PBDiggins,

I wanted to follow up with you, and see if you were able to get the HVAC specialist to take a closer look at your system. Please let me know if they were able to help resolve the issue, as I want to ensure you are good to go.

Best regards,

Jake

[Jake]

Hey PBDiggins,

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Best regards,
Jake

[Jake]

Hey PBDiggins,

I am glad to hear that you will be having someone come and take a closer look at the system. I am going to keep the thread open for a few more days to ensure everything works out. Please feel free to reach back out, if you have any more details. 

Best regards,

Jake

[Jake]

Hey PBDiggins,

I wanted to check in with you, and see if you were able to get someone to take a closer look at your system. Please let me know, as I want to ensure you are good to go.

Best regards,

Jake

[PBDiggins]

Thanks for checking. It might be a few weeks before we get the HVAC specialist to come back.

[PBDiggins]

Hi - This is on hold while our building negotiates some broader HVAC issues with the HVAC company. When they visit for those repairs we're going to have them investigate the current thermostat wires and ideally upgrade to our Nest. Thanks.

[EdwardT]

Hi PBDiggins,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward