A while back, I thought we finally answered the C wire questions once and for all. I took a bit of time and wrote up this answer, which was going to allow us to close all other C wire questions as a duplicate.

Since then I've answered quite a few C wire questions, some of which have stated "I've read this answer, but I still don't know where to connect my C wire". Out of all the questions I've answered about the C wire, there have been probably only one or two that were more complicated than what was covered in my answer.

Does my answer need more information, more updates, or maybe a complete rewrite? Should we just close all "Where do I connect my C wire?" questions as duplicates, or do we continue to answer them all?


Too many to list, just use this search.

3 Answers 3


I agree that they should all be marked as dups. I'm not seeing added value from all the extra posts, and it sets a bad example for other questions where people don't understand why one question is a dup but another isn't.


TL;DR, teach people how to read their own schematics (is it safe to do so? IDK: for some it will provide a false sense of competence; others it may save their life).

Begin wall of text:

That answer is comprehensive but on it's way too becoming to broad, especially if you take my suggestion of somehow adding more information about how to read a schematic and how to apply it to the real world.

If people knew what they were doing they wouldn't have to ask, and they certainly don't know what to say over the phone to the manufacturer:

"...and may not be approved by every manufacturer. Check with the furnace manufacturer..."

People ask a new question because they want you to answer this; here's my model numbers, now do the math please... (and draw me one of those nifty-colored-idiot-prof diagrams for my furnace).

If I had a schematic of anything I didn't understand, I'd bring it before you, regardless of on-topic or not. Because you're really, really good at understanding them and making people understand them (+1 for non-hand drawn red circles).

Final answer:

No. They keep making new and different ones; you're gonna have to keep drawing red and blue lines on people's specific schematics.

Apples and oranges:

What size wire for my garage?; now, that's been put to bed I hope. At least that doesn't keep changing, like thermostats and furnaces. I have one good question here, How To Do Tile. I asked it partly because it seemed that no one else had, and as a go-to for: all of your concerns are answered here. For tile you can pretty much get away with that; electrical schematics, not so much.

Admittedly though, I did not ask my question to close dups... It's more for leaving a comment: see here, or for a short answer with: further reading.

Feature request:

A 'hold' on questions that can be lifted by the OP, by simply editing the post or something like that.

Your question has been placed on hold because it is believed to be a duplicate of this question. If the answers to that question do not provide a solution for you, click the button at the bottom of that page to re-open this one.

This may just be a roundabout way to deal with my pet peeve of post abandonment, but it'd be a good way to make people read that other question, and it be OK when they don't come back to their own; it'd have been dealt with: on hold and on its way to being closed. Also, it should only require X rep; not 5 people seemingly ganging up on some poor new user, for which they can basically do nothing if y'all think it's a dup.

Extra credit:

Stack Exchange exists as a repository of Q&A's; it's main goal. However, to usefully achieve that goal it must help people to understand their specific situation ("please explain to me..." -the FAQ).

Until we have addressed Every Single Possible Conundrum Ever, our work is not done.

I ask you:

(out of sheer boredom at this point)

When you close a C wire question as a dup, did you pull up the schematics of their equipment and verify that it is indeed answered elsewhere, or do they still need to verify that with the manufacturer? If so, your entire answer is useless to the common noob; information-overflow.

Don't get me wrong, it's an excellent answer to Google across, but not if you need the concepts behind the concepts explained to you: i.e., reading schematics... (and as expressed in meta questions concerning safety, you should not be explaining electrical concepts to novices anyway).

Finial note:

I realize that is what your answer has tried to accomplish; teach furnace schematics. But what it really needs is real world pictures showing where the things on that diagram are. Which will however be different for each person's unit. So again: no.

  • It seems like most folks don't know how "closed" questions work. When a question is placed "on hold", if the OP edits the post in any way, it's automatically moved to the "Reopen" review queue. Once there, privileged users can vote to leave it closed, edit it further, or reopen it. So basically the system currently works as you've described, except that there's not a button to press to activate the reopen process.
    – Tester101
    May 15, 2015 at 10:50
  • 1
    The answer I've provided tries to teach the reader just enough about schematics, so that they can potentially locate the transformer in their own schematic. Though it sounds like either I've failed, or I've provided too much information and folks eyes are glazed over as they read it.
    – Tester101
    May 15, 2015 at 10:55
  • @Tester101, it does work as described, but modifying it places it in a queue; not re-opens it. From a new user's perspective, 5 people voting to hold or close (see, I still don't even get it fully) means to the OP, your question is answered elsewhere, you just don't get it, and until you understand how SE works or more about your own problem, we can't help you. -continues...
    – Mazura
    May 16, 2015 at 0:51
  • What I'm asking for is similar to another feature I'd like: OP approved edits. With this new one, the OP can decide: no, I still don't get it. Please explain it to me. It would avoid editing the question to add: I've read that 'dup', still nothing..., to get it reopened. -I've digressed, your answer needs to just show the symbol for a transformer, and its real world equivalent. Also note that question specifically asks how to add/pull/swap-the-use of a C wire, not how to hook it up and where. There is no end-all for how. I.e., YMMV.
    – Mazura
    May 16, 2015 at 0:51

Before you mark everything as duplicate maybe you should make sure that you have a "Master" C wire answer that goes over all of the good points you have made in the past. I have probably answered 30 questions on how to set up a shower/tub for tiling but the content is probably only 70-80% the same across the questions. Maybe for questions that are similar that have more than X amount of accepted answers there should be a "Master" question/answer.

This would probably require the author to consolidate their good points to one question, to make sure that the question was asked in a generic enough way to capture most other questions, and possibly for SE to recognize that as a "master" question/answer.

Also I would think... what would I do if I had a C wire question? Well I would probably read through your answers. But you have a lot. If I didn't see what I needed in the first 5-10 I would probably add onto your list of questions. Maybe you never answered my specific oddity. So how would I as a user (even knowing there is a master question/answer that everything is getting closed to - which most users won't know this) communicate with Tester to ask their one off question? You could do it in comments but then that limits the question in the comments to being answered by Tester. And if Tester quits SE cold-turkey then I have a floating question in comments never answered.

  • 1
    And what is funny is that I am working on a new house with a C wire issue. I might be asking a question soon!
    – DMoore
    May 11, 2015 at 18:56
  • I guess part of what I'm looking for with this thread, is to find out what's missing from the "master" answer that I've provided.
    – Tester101
    May 11, 2015 at 19:09
  • 1
    The problem I see, is that everybody thinks their question is a oddity. However, if you actually understand how the system works and how to read a schematic, you'll see that the questions are all very similar.
    – Tester101
    May 11, 2015 at 19:12
  • @Tester101, That's the problem; see my answer.
    – Mazura
    May 15, 2015 at 3:41

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