I have an older nordyne Furnace and am trying to install central air. My question is hooking up the thermostat, there are no wires to add on for a 4 wire system, do I need to install the optional transformer for this like the wiring diagram shows? Thanks

Is this unit in a mobile home?

Yes it is.

This could be a problem. If the furnace did not come with the A/C blower and control package you usually have to add it. This can get expensive since all the circuits are located in the A/C blower and control package to allow just the two wires you now have to control both the heat and A/c. I am listing a link below. These guys are mobile home professionals and have a great help site. Post your question under the Nordyne service and repair area. They might have a easier solution.

Index page (http://www.mobilehomerepair.com/phpbb/index.php)

This will give you an idea of the blower motor A/C conversion and control box.

Thanks for the information. Do you think I could wire in my own Fan Center Relay to do the job? Thanks

If you plan on running new 5 wire thermostat cable then you just might get buy with a honetwell or White Rodgers fan center but if you are going to try and duplicate the factory setup to stay with the two wire setup good luck since there a at least two different relays a special rocker switch for A/C off Heat positions etc.

Thanks a lot, I am running a new 5 wire, just wanted to get an experts thoughts, I'm glad there are people like you willing to help help others out.
Thanks again.

No problem