I am looking to install a new style thermostat in my apartment and it requires a C wire.

I do have an extra wire run from my HVAC unit to where my thermostat is. But when tracing it back to my HVAC unit it is not plugged into anything.

So I was wondering if anyone could help me figure out where to put it in the HVAC unit to use as a C wire.

Here are two picture of what I am looking at. I wish it was as easy as plugging wires into a circuit board but it seems my system is a little out of date in that regard.

Any help is much appreciated! I can post more pictures if needed.

Update 2:

enter image description here enter image description here

  • 2
    Do you have a wiring diagram on your system that you can post a picture of? – ThreePhaseEel Oct 2 '16 at 18:49
  • I do not. Is it impossible to figure out without it? – Colin Oct 2 '16 at 19:01
  • Can you take a photo of your 24V transformer then? – ThreePhaseEel Oct 2 '16 at 19:05
  • Okay I updated it with what I believe you are asking for..hopefully it is good enough quality – Colin Oct 2 '16 at 19:19
  • Hrm...it seems your transformer is mounted quite awkwardly...can you get a better photo of how it's hooked up? – ThreePhaseEel Oct 2 '16 at 20:11

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