My house has a Janitrol dependable 92 furnace. I would like to upgrade my thermostat, and the new one requires a "c wire" connection. I have an extra wire in the bundel that conects the t-stat to the furnace that I would like to conect, but when I opened the furnace there in no obvious "c wire" connection point. Wondering if someone has a wire diagram for this furnace and can tell me wich wire from the furnace should be connected to the c wire of the new t-stat.

The C post on your new tstat is for a common wire which is used when you want the tstat to be powered from the furnace and there will be no need for you to use batteries in the tstat. The extra wire that you have at the tstat can be tagged to the c post and the other end is tied or spliced to a wire (usually blue ) in goodman furnaces that that is grounded to the cabnet in the area where circuit board is located

It's either on the board or there's a wire that is used as the 24 volt common. There should be a diagram on the backside of the door?? Most likely with Janitrol or Goodman of that era there was no common terminal at the board and it was simply a wire hanging there.

OK, I am trying to do the same thing here. I have a gmpn080-4 Rev B. I want to install a new T-stat that is in need of a "c-wire". I have an extra wire in my bundle. I get the t-stat part, but I am not sure where to hook it up on the furnace. I don't see a c-wire connection on the main board anywhere, so I am not sure where to connect it.

wmproop, are you saying I can just hook this up to the ground and that will work? That doesn't seem right, but I am not the greatest at this stuff.

Here is my wiring diagram, it's the last page: http://www.alltemp-hvac.com/gmpn.pdf

Thanks for your help.