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Discussion Starter · #1 ·
I have a GE Ambassador Mark II from the early 80s (still going strong). I was installing an Ecobee3 and ran into the C-wire issue. Blue C-wire is there, but not hooked up to the furnace. Please see pic below. Looks like I have two options: connect to blue or connect to black.
 

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The blue wire is what we in the trade refer to as a common if you have batteries in your stat it doesnt matter whether the "blue/ C is hooked up. If your furnace ran before without the common it still should. It will draw a common From transformer to relay. All the blue does at stat is complete the 24v circuit @stat. Through some batteries in stat and roll out....
 

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Discussion Starter · #5 ·
Success!!

With that little bit of insight from Supers05 about making sure to pull from low voltage side of the two wires coming out of transformer, a picture of a blue to blue connection on an 8 year old pic posted on another forum, and a little bit of courage, I took a chance on the blue to blue connection. Now my 30-year old furnace and state of the art Ecobee3 are totally rockin'!

Thank you very much from Northern California, where nights are in the 30s F this winter.

I wish you all a fortunate new year!
 

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Hi,
While performing and internet search I came across your post. I too have a GE Ambassador II gas furnace (with no modern program board) that is still going from the 80's and would like to install an Ecobee, Honeywell or Nest and they all require the C wire hookup. Based on your experience could you please detail more of the path of success you took? I am close to understanding but need a little more helping hand and I would very much appreciate it.

Also, since your posting have you been pleased with the Ecobee?

I currently have a Honeywell Chronotherm III that is programmable but recently the LCD display was going out, changing the 3 AAA batteries helped but I thought I might as well go ahead with something my wife could control from her phone for more convenience and enjoyment.

Thank you for any further details and/or links you can offer.

Please post or pm me, I am unable to PM you as I am new to the forum and do not have the amount of posts required I guess. Thank you.
 

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Hi,
While performing and internet search I came across your post. I too have a GE Ambassador II gas furnace (with no modern program board) that is still going from the 80's and would like to install an Ecobee, Honeywell or Nest and they all require the C wire hookup. Based on your experience could you please detail more of the path of success you took? I am close to understanding but need a little more helping hand and I would very much appreciate it.

Also, since your posting have you been pleased with the Ecobee?

I currently have a Honeywell Chronotherm III that is programmable but recently the LCD display was going out, changing the 3 AAA batteries helped but I thought I might as well go ahead with something my wife could control from her phone for more convenience and enjoyment.

Thank you for any further details and/or links you can offer.

Please post or pm me, I am unable to PM you as I am new to the forum and do not have the amount of posts required I guess. Thank you.
What part are you having trouble with? There are only 4 wires to the transformer. 2 for high voltage, ignore those.

2 for low voltage. 1 will end up at connecting with your red "R" wire. (often but not always, it will be fused first.)

The other wire may be connected directly to the chassis of the furnace or gas valve. This is your common wire. You can connect directly to it with the thermostat wire.

You'll need 5 posts before you can posts pictures of your wiring.

You'll also likely need to pull a new wire from the thermostat to the furnace.

Cheers!
 

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I couldn't sign in to my original account so I created a new one.

Patrick, if your Mark II is like mine, there will be two blue wires at the bottom of the furnace. I was confident that I picked the correct one because I followed one of them to a connector thingy that was marked 24v. It wasn't an super obvious mark, but it does say "24v" on mine. This is at the furnace itself (please see the picture that I posted at the beginning of this thread).

The Ecobee 3 has been great. I had a wifi issue a few months ago, but a quick call to tech support and they solved the problem easily and expertly over the phone. I haven't used it with Apple Home, since the app that comes with it does the job perfectly. The touch interface at the thermostat is way better than the turn dial interface of the Nest. Also, the remote sensor is a real difference maker; the temp difference between my bedroom and the rest of the house can be as much as 7 degrees Fahrenheit in the winter. This saves money as well as ensuring that I am sleeping at my ideal temperature and not in a sauna.
 

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Of course my thermostat decided to completely die last night. Temp outside is 10deg and we get to enjoy below zero temps for the next 10days.

What part are you having trouble with? There are only 4 wires to the transformer. 2 for high voltage, ignore those.

2 for low voltage. 1 will end up at connecting with your red "R" wire. (often but not always, it will be fused first.)

The other wire may be connected directly to the chassis of the furnace or gas valve. This is your common wire. You can connect directly to it with the thermostat wire.

You'll need 5 posts before you can posts pictures of your wiring.

You'll also likely need to pull a new wire from the thermostat to the furnace.

Cheers!
Thank you, I do have additional wire to the stat, two actually low voltage, 1 blue 1 black. Using the posts here today as added guidance.


I couldn't sign in to my original account so I created a new one.

Patrick, if your Mark II is like mine, there will be two blue wires at the bottom of the furnace. I was confident that I picked the correct one because I followed one of them to a connector thingy that was marked 24v. It wasn't an super obvious mark, but it does say "24v" on mine. This is at the furnace itself (please see the picture that I posted at the beginning of this thread).

The Ecobee 3 has been great. I had a wifi issue a few months ago, but a quick call to tech support and they solved the problem easily and expertly over the phone. I haven't used it with Apple Home, since the app that comes with it does the job perfectly. The touch interface at the thermostat is way better than the turn dial interface of the Nest. Also, the remote sensor is a real difference maker; the temp difference between my bedroom and the rest of the house can be as much as 7 degrees Fahrenheit in the winter. This saves money as well as ensuring that I am sleeping at my ideal temperature and not in a sauna.
My Mark II is like yours, I will seek out the 24v label also, just one more check won't hurt. No choice but to pick up a new thermostat today. Thanks for your feedback on the Ecobee.

When I get home I'll take a pic of the wiring and post it here.
If you get your old account working and happen to post the picture, any additional help is always welcomed.

Thanks you guys, I appreciate you posting to the older thread, you've been great!
 

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Success. Came home today during my work break, quickly installed a general programmable. Returning after work, connected the C cable to the 24v relay and instead installed the Ecobee3 and will see how we like it.
Hope everyone stays warm for the holidays and thanks again for the help.
 
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