M1MB nordyne furnace to thermostat and ac wiring

[Tinamblank]

M1MB070ABW nordyne furnace, S3QA-036KA miller ac, 9500 robertshaw thermostat... What is the correct wiring for the yellow thermostat wire (cool) and the grey furnace (24vac common) to the ac contractor coil? The coil ohms good at 16 ohms, the thermostat is shorting the red to the yellow and green (fan) wires (measured at the furnace), furnace fan is a no go and the compressor is not starting. 5 minute compressor wait time works in 9500 thermostat. Rh and Rc jumped at thermostat, no other jumpers. When I purchased the house, the ac coil wires were just dangling inside the furnace cabinet. Heat works great. Am I missing a part? Or should I just be able to wire the coil to the yellow and grey wires? Thanks for your help! The manuals don't show past the dangling wires either!!!

[DaleM]

You should be able to re-connect those wires from the AC contactor to Y and C (grey) in the furnace compartment. Someone may have taken those out of the system because of a problem they could not troubleshoot out. Maybe the fuse on the board was frying when the wires were connected. If that's the case look for chewed or shorted t-stat wiring under the home from the furnace to the AC unit. Might want to have some of those fuses on hand before you start on it.

[Tinamblank]

I think I blew the 3amp fuse myself when I hooked the grey wire to the yellow wire and then tried to start the cooling cycle thereby shorting out the secondary of the transformer. Last nite I replaced the fuse and hooked the grey wire to one side of the contactor coil and the yellow to the other side a voila! It works! One more question; the 3 sPeed fan has the heat set for Medium speed and the cool spade terminal is wired to the low speed wire to the fan as per the diagram in the manual??? BUT the manual diagram also states to check the table for the 070 with the B (3ton) meaning that the cool should be on the high speed wire? Maybe they were having an ice up problem in the coil with the 3ton unIt running the furnace fan on low? Any thoughts? I've set it for hi speed for the cooling fan per the table in the text part of the manual. I also think I need the special fully luvered closet door for this Particular install as the front of the furnace intake panel is only 2inches from the closet luvered door which only has luveres half way down the door and an additional 8inches at the bottom. Do you carry these closet doors? And I was also thinking of adding the electrostatic airecare air filter pn 903603 to my furnace? Any opinions and do you carry this part? Thanks for your reply!

[DaleM]

The only parts I sell are what we install. No outside sales. As for the furnace door look for something like a louvered bifold door at Home Depot, Menards, Lowes etc. As for the fan speeds the original installer of the home or unit should have checked those and set them according to the manual. Sounds like you have it right now, medium speed for heat and high speed for a/c. Stay away from the electrostatic filters. The basic 16 x 20 filters work fine. You may need to trim them a bit but they are perfect for the mobile home furnaces. Keep in mind these systems have no return air ducting system like residential systems. They depend on the blower being able to pull ample air in through the front of the furnace. Filters that are too restrictive limit air flow cutting heating and cooling efficiency.